Plumeria Seeds and Seed Quality

Seed quality plays an important role in the production of quality plumeria and plumeria used for root stock. Characteristics such as germination, germination percentage, vigor, and appearance are important to growers planting plumeria and to homeowners establishing plumeria gardens. Achieving and maintaining high seed quality is the goal or should be the goal of every plumeria seed producer.

Seed Development and Structure

Seed Development

The process of seed development begins within the flower, the plant’s reproductive structure. The plumeria flower is both male and female. The female part is the pistil, and the male part is the stamen.

The pistil has a top portion (stigma), a middle portion (style), and a lower portion (ovary). The ovary may contain one or more ovules. The surface of the stigma produces a sweet, sticky solution as it becomes receptive to pollen fertilization.

Pollen is produced in the anthers at the ends of the stamen. Pollination occurs when pollen grains come into contact with the stigma. Wind and insects are largely responsible for the transfer of pollen from the anthers to the stigmas.

If conditions are favorable, pollen grains begin to grow on the stigma surface and form pollen tubes. The pollen tube grows down the style and into the ovary, where it comes into contact with the ovule. Male gametes are transferred through the pollen tube into the ovule. Fertilization occurs when the male gametes unite with the female egg in the ovule. After pollination and fertilization, ovules develop into seeds.

In self-pollinated plumeria, pollen produced within each flower pollinates the stigma of the same flower.
In cross-pollinated plants, the pollen grains pollinate flowers other than the one from which they originated.

Fertilization occurs shortly after pollination and begins the process of seed development. Early stages in the development of strong plants depend on favorable growing conditions. Seed quality, on the other hand, is largely dependent upon environmental conditions and the promptness with which the seed is harvested after it matures.

Seed Structures

Knowledge of seed structure can help in understanding how seeds respond during germination, and seedling emergence.

Seeds can be divided into two major classifications, monocots (monocotyledons) and dicots (dicotyledons), based on the number of cotyledons (seed leaves) in a seed. Monocots contain one cotyledon, whereas dicots have two. Plumeria are dicots.

Seeds are composed of three basic structures:

(1) the seed covering (seed coat or testa);
(2) the embryonic axis (embryonic root or radicle and shoot or plumule); and
(3) supporting tissues (the cotyledons and endosperm).

If unbroken, the seed coat regulates water uptake by mature seeds. The seed covering characteristics often affect the quality of seed when exposed to adverse weather. Some seeds, such as plumeria, have a soft and semi-delicate seed covering. This covering can easily break or slip and expose the embryo, making it susceptible to injury, deterioration, and pathogen attack.

The embryonic axis normally includes the miniature plant, consisting of the root and shoot. Cotyledons and endosperm are usually considered supporting tissues. They are useful to the developing plant as a reserve food source through the course of germination and emergence until the plant can make its own food through photosynthesis. Supporting tissues in dicots are composed of mostly fats and oils.

The location of seed structures plays an important role in determining the seeds’ susceptibility to mechanical injuries and weather damage. The embryonic axis is often just below the seed covering. Impacts to the embryonic axis can cause severe damage, resulting in abnormal seedlings or death of the seed. Plumeria seeds can survive for years, but the germination rate declines over time.

Figure 1. A typical flower. It may contain both the pistil (female) and stamen (male). Many flowers contain only one pistil but usually several stamens.

Sizes and Shapes of Seeds

Plumeria Seeds come in many sizes. They range in size from the small to large. Shapes are similar all with a wing.

Dispersal Mechanisms

The dispersal mechanism of plumeria seeds is as simple as dropping of the seed from the parent plant onto the ground to the more exotic ways such as scattering by wind from the plant.

Chemical Composition of Seed

Like all living organisms, seeds are composed of many different types of chemicals, but seeds are unique in that they are a storehouse of chemicals that are used as food reserves for the next generation plant.

Seeds store three major classes of chemical compounds: carbohydrates (sugars), lipids (fats and oils), and proteins. The quantities of these compounds stored in seeds vary with the type of seed.

Proteins are made up of long chains of amino acids. Most seeds are not high in protein but are high in carbohydrates or lipids. The seeds of most plants store their food reserves mainly in the form of carbohydrates or lipids.

Germination and Field Emergence

The following definitions will help in understanding seed germination and seedling emergence:

Germination is the emergence from the seed and development of those essential structures that under favorable conditions produce a normal plant. Germination is more than just the protrusion of the root or shoot from the seed covering. It is important that all of the seedling structures necessary for continuation of the next generation be present and healthy.
Field Emergence is the elongation of the seedling axis resulting in protrusion of the seedling shoot from the soil.
Viability is the potential to germinate. A nonviable seed will not germinate under any conditions. Viable and a nonviable seeds may look exactly the same.
Dormancy is the state of nongermination in viable seed. During this period, germination is blocked by conditions within the seed. Dormant seeds are often thought of as being in a resting state. Dormancy is broken when the plumeria seed is exposed to warmth and moisture. A seed may take up water and look fully able to germinate but, because other necessary conditions are not present, may fail to germinate. If a seed starts to germinate and is deprived of moisture, it may stop the germination process and die.

Germination

Requirements for initiation of germination include:

a favorable moisture level in the seed;
a favorable temperature in the environment around the seed;
a favorable oxygen supply to the seed.

Note that favorable conditions must be present. Plumeria seeds do not require light conditions.

Germination occurs in several steps. The first is the absorption of water. Water begins certain biochemical processes within seed that accelerate cell activities. The minimum moisture level at which germination begins is known as the critical moisture level.

Critical moisture levels vary among crop seed. Most dicots will not begin germination until they have a moisture content of at least 50 percent.

Germination will not occur above or below the critical temperatures. Each species has a minimum, an optimum, and a maximum temperature for seed germination. Most species have a minimum germination temperature of approximately 55°F (13°C) and a maximum germination temperature of approximately 110°F (43°C). The optimum temperature is usually from 75 to 85°F (24 to 30°C).

Lack of oxygen is not usually a limiting factor for germination. However, wet or soggy soils may not contain enough oxygen for germination to begin. Seeds planted in such soils will absorb water quickly and have a tendency to decay.

Plumeria seeds germinate equally well with or without light.

The internal conditions of seed, such as soundness and vigor, as well as the environment, affect the rate of germination. Seed vigor can be affected by maturity, age, mechanical injuries, disease infection, preharvest weather, and storage environment.

Adverse weather conditions after planting regularly influence the germination processes by affecting moisture, temperature, and oxygen levels.

Once cell activity is initiated, the root is the first structure to emerge from the seed coat. Root growth is a result of both cell division and elongation. Hypocotyl growth is mainly a result of cell elongation. Shortly after root growth begins, the shoot meristem emerges from the seed coat and continues development by cell division and elongation.

Field Emergence

Different species exhibit different seedling emergence patterns.

In plumeria, root growth occurs by cell division and enlargement of the root (Figure 3). As growth continues, the hypocotyl elongates by cell enlargement, and the midsection emerges from the soil (Figure 3). The seed coat usually remains below ground. As the bent hypocotyl elongates, it gradually pulls the cotyledons above ground (Figure 3). During the critical stage when the hypocotyl is still arched above ground and is pulling the cotyledons upward, damage to the hypocotyl can easily prevent seedling emergence.

Figure 3. Field emergence pattern of soybean seedlings.

Seed Vigor

Seed vigor is the property that gives seed the potential for rapid and uniform emergence and development of normal seedlings under a wide range of conditions.

Many factors, such as maturity level at harvest, age of the seed, mechanical injuries, disease infection, and storage environment, can influence seed vigor. Genetic factors also influence vigor.

Seed Quality

Quality Characteristics

Seed quality describes the potential performance of a seed lot. The presence of inert matter, germination percentage, vigor, appearance, and freedom from disease are important aspects of seed quality. High-quality seed lots should meet minimum standards for each of these characteristics.

Trueness to variety indicates that the seeds in a bag are of the variety stated on the label. Trueness is usually determined by the trustworthiness of the seller and the grower.

Germination potential and vigor are at their highest potential when the seed reaches physiological maturity. It is important that seed be harvested as soon as the seed pod matures and opens. After maturity, germination potential and vigor begin to deteriorate.

The rate of deterioration depends on the weather at maturaty, harvesting, conditioning, and storage practices. Seed can deteriorate rapidly if excessive damage occurs during harvesting and conditioning.

If seed moisture levels are higher than those recommended for safe storage, the seeds should be allowed to dry out before storage. Seed storage conditions, which can also greatly affect deterioration rates, is discussed in more detail in a later section.

The quality of a seed lot can be improved by conditioning. Conditioning is used mainly to eliminate or reduce undesirable contaminants such as excess moisture, fungus, broken or split seeds.

Chemical Seed Treatment

Pathogens (organisms that cause disease) are often present on or in the seed. These organisms can cause diseases that destroy the seed or seedling. Chemicals applied to the seed can prevent or reduce the harmful attacks of many pathogens. These treatments include fungicides, or insecticides.

Fungicides are chemicals that are normally used to combat seed rots, surface molds, and seedling blights caused by seed- and soil-borne organisms. The ideal fungicide should be highly effective in controlling a specific disease organism. Insecticides are used to protect the seed from soil-borne insects and storage insects. Some treatments combine a fungicide with an insecticide to protect the seed against soil insects and disease organisms. The chemicals used should be harmless to seed, stable for long periods of time, easy to use, and low in toxicity to people and animals.

Systemic treatments are absorbed by the seed or developing seedling. These treatments protect both the seed and the young plants against diseases. For example, Baytan, a seed treatment that became commercially available in 1990, protects plants from many foliar diseases (including powdery mildew and rust) for up to eight weeks after seedling emergence.

Treatment chemicals are formulated as dusts, wettable powders, or liquids. A critical problem is obtaining uniform and adequate chemical coverage on each seed. Undertreatment is ineffective and overtreatment may injure the seed; therefore, accurate metering devices are necessary to dispense the proper amount of chemicals to a given quantity of seed.

Storage

Plumeria seeds are stored for some period of time. During this time, seed may deteriorate considerably. Good storage conditions can slow the rate of deterioration, but seed germination and vigor cannot be improved, regardless of the storage facilities.

Many costly storage problems actually begin during field exposure, harvesting, and conditioning of the seed. Excessive harvesting delays, mechanical injuries, and improper drying techniques, followed by poor storage conditions, can lead to rapid deterioration of seed germination and vigor.

Longevity of Seed in Storage

Different species of seed have different storage lives. The storage life of plumeria seeds ranges from several weeks (as in some tropical tree species, whose seed loses viability when dried) to several years (as in the case of the plumeria rubra and obtusa).

Typically, the storage life of plumeria seeds ranges from 1 to 5 years under ideal storage conditions. For example, plumeria seeds have been stored in ideal conditions for as long as 10 years. Plumeria species seeds are not normally carried over from one planting season to the next, while Plumeria rubra may be stored for several years if stored in the proper environment.

Seed Deterioration

The general pattern of seed deterioration is approximately 10% per year. Germination remains unchanged for a period of time during storage and then declines rapidly.

As seeds age, both germination and vigor decline, slowly at first and then more rapidly as the end of the seed’s useful life is reached. Vigor declines faster than germination.

Storage Conditions

Deterioration is slowed when seeds are stored under cool, dry conditions. Temperature and relative humidity should therefore be considered in planning for safe storage. A rough rule of thumb for safe seed storage is that the sum of the temperature (°F) and relative humidity should not exceed 100 units. For example, if the temperature is 60°F, the relative humidity should not be over 40 percent.

Seed moisture is the most important factor affecting seed longevity. Seeds adjust their moisture content until they are in equilibrium with the surrounding storage environment. Temperature and relative humidity affect the amount of moisture in the air and will influence the equilibrium moisture content of seed. A general rule is that each 1 percent decrease in moisture content of the seed nearly doubles the safe storage period. Thus it is important to put dry seed into storage and keep it dry.

Choosing Seeds

Seeds usually represents a relatively small part of the monetary cost of adding to your plumeria collection. Generally, the investment is less than 2 percent of a plumeria plant. Keep in mind that plumeria seeds do not produce true to its parents.

What factors should be considered when choosing seeds? Each quality characteristic is important. When you are buying seeds, you should establish an acceptable quality level for each characteristic.

The first step in choosing seeds is to select seeds from a known trustworthy seller. The importance of this decision cannot be overemphasized. The seller choice and the quality of the seed set an upper limit on yield and quality.

Seed dealers can use many aids to help customers select cultivars most likely of producing desired results in the seedlins. In addition, seed dealers should have a record of the parents and may have information on the lineage and seedling produced by the parents.

Varietal purity cannot be determined by laboratory tests. Purity can best be determined by keeping accurate records of production and relying on customer feed back. Your best assurance of varietal purity is through the use of seeds from named parents.

Seed parentage information can reveals some of the important characteristics to consider in choosing seeds. It is difficult, however, to establish definite standards for these characteristics. The general rule is to choose seeds from parents that have a history of producing quality seedlings and have a high germination rate (above 70 percent).

Germination and other soundness characteristics may vary from season to season, In many cases, seed growers have to accept the germination and soundness quality available. It takes careful searching to find the best seeds.

The reputation of a seed wholesaler or local producer is rated in relation to the quality of seed sold. Retail seed dealers should patronize those wholesalers who most consistently supply high-quality seed.

Dealing with companies that specialize in “bargain” seed often proves embarrassing and costly to the grower. The initial price of bargain seed may appear low, but it frequently becomes very costly by the time your seedling blooms.

It is never a good practice to purchase or plant seeds if at least one parent’s information is not available.

Planting Good Seed

Damage done to seed while planting is often overlooked. Seed size varies considerably within and between cultivars and even between varieties, so it is a good practice to check each seed for viability.

Soil preparation is also a part of good planting practices. A smooth, firm seedbed will permit uniform seeding at proper depth. Uniform planting depth is important for a uniform emergence pattern. Depth settings are especially critical with multiple-row planting equipment.

Analyzing Germination and Keep Records

Problems should be analyzed in three general areas:

(1) the seed;
(2) planting procedures, including such things as planting equipment and methods, use of chemicals, and fertilizer placement; and
(3) weather and soil conditions at planting and shortly thereafter. In analyzing seedling establishment problems, all possibilities should be considered.

It is important that the facts in each case be gathered as soon as possible. It is difficult to obtain reliable information about seed problems after the plumeria died or has been sold.

Adverse weather and soil conditions can cause seed failures. Widely fluctuating temperatures or moisture levels during the seed germination period can affect seedling emergence. Under these conditions seed failures may be variable if the growing containers contains several soil types.

Soil insects and insecticides create germination problems in some crops. It is always a good practice to read the labels of any pesticide applied to the soil or young seedlings to prevent harmful side effects.

It is critical that information about all chemicals and rates be examined. Some soil fumigants require a waiting period before crop seed can be planted safely. If these intervals are not observed, slow germination and spotty emergence may result. Previously used soils may have herbicides used on previous crops may cause carryover injury. Always read pesticide labels carefully, and follow all directions.

Make it a practice to use quality seed tags for all seeds planted.

Summary

Seeds are complex, living organisms that play a very important role in producing new plumeria cultivars. High-quality seed lots of adapted varieties are the result of breeding, research, and careful management during all phases of seed production.

Consider seed selection as the first step in production. Cultivar selection and seed quality set the maximum performance level for all plumeria.

Anyone purchasing seed should:

choose cultivars that are well suited your desired plumeria characteristics
read the seed parents history carefully, avoiding seed with no parents specified and those with low germination
plant the seeds when soil conditions are favorable, thus promoting rapid germination and seedling growth.

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Plumeria Seed Pods

Plumeria seeds form when a flower is pollinated either by the wind (self pollination) or by an animal, hummingbird, butterfly, thrip, sphinx moth, tiny ants or by human. Once pollinated, plumeria flowers will fade and begin to grow into seed pods. Plumeria seed pods grow from flowers pollinated during the previous growth season. A single pod may contain from 25 to 60 seeds and usually grow in pairs. When the seed pod is growing you can wrap it loosely in cheesecloth to catch the seeds when it splits open. Do not wrap it so tightly that you block the circulation of fresh air.

Plumeria seed pods take about 9 months to mature. After they mature they will crack open and the seeds will be disbursed by the wind. If you harvest before they are ready, the seeds won’t have a chance to mature properly and most likely will not be viable.

Collecting Seed pods

Seed pods look like two long beans. They can be green or light brown to dark brown. Different cultivars will product different looking and sizes. From the time they start growing to the end of their growth, they may reach 12 inches long or more. Seed pods will continue to grow over winter storage while their plumeria is in dormancy. So watch them during the winter, the growth is slower, but they could still open if they mature during winter storage.

When the pod start to discolor and look like they are dying, they are getting ready to open. When you see the seam along the seed pod start to crack, it’s time to cover. A netting material or stocking is good to cover the seed pod and capture the seeds. The netting will allow them to continue to receive water and sunlight through the openings. Place the netting or stocking over the seed pod giving it plenty of room to breath and open fully.

Most plumeria seed pods open during the spring, but the seed pods will open all year long, depending on when the bloom was pollinated. Once they have opened, your cover will catch the seedlings. It is ok, to pick the pod if it has started cracking open. Place in a cool dry place and it will fully open in a few day. After it opens allow the seeds to dry out for a few days. Moisture can cause bacteria or fungus to grow.

After they have dried you may either store them in a dry dark place or plant the seeds. Some plumerias are great seed pod producers, some may only produce a few a year while other may never or very seldom produce seed pods. Some seed will do better if you plant right away. Seed Pods have been know to stay viable for 10 or more years, but the average is more like 3 years. Regardless the seeds germination rate will decrease over time.

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A Guide to Growing Plumeria From Seed

Posted on January 29, 2018January 29, 2018 by GrowingPlumeria

I’ve been using FlexiPlugs by Grow-Tech for the last four years to germinate seeds and grow seedlings for the first phase of root growing, with very good results results. I would like to share my experience with this Guide. Click on this linke to find out more about how I use them. My methods may need to adjusted to your growing environment. https://plumeriaseeds.com/guide-growing-plumeria-seed/

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How To Germinate and Care for Plumeria Seeds and Seedlings

At first glance, a seed appears to be just a small, simple thing. But hidden inside is the potential for a unique and wonderful plumeria that may take the world by storm. Inside each seed exists all of the genetic information needed for that plumeria to grow throughout its entire life cycle and its destiny is retained inside that little seed.

Plumeria Seeds

When germinating plumeria seeds at home or in a greenhouse, the first thing to remember is plumeria seeds may be started indoors, but should be transplanted and moved to a location that provides plenty of light as soon as it has 3 or 4 real leaves. Leaving a seedling in small containers may result in disrupted growth, which can lead to unfavorable results. However, starting plumeria indoors is a great way to get an early jump on the outdoor growing season. When choosing a medium in which to germinate plumeria seeds, look for one that says something along the lines of, “seed starting mix.” This type of growing medium will likely have a moderate elemental fertilizer charge, which will benefit the newly sprouted seedlings. Seeds can be germinated in many different styles of trays and containers, so choose the type that best fits your space needs. If starting just a few seeds, a simple, flat starting tray or small individual containers will work great. When planting many seeds at once, it may be wise to use trays that are divided into separate growing chambers. This will cut down on the amount of transplanting needed as the plants grow. Remember, all a plumeria seed needs to germinate is warm temperatures and moisture. Some growers do use heat pads underneath the starting trays. Most plumeria seeds will germinate at temperatures between 65-90 degrees Fahrenheit and the added warmth in the growing medium can speed up the germination process. Using supplemental lighting, like a T5 fluorescent bulb, can also help provide extra heat. Though seeds may not need light in order to germinate, the seedling will need light, so having a light source ready is a good idea. I would use caution when starting seeds in a bright window sill because direct sunlight through glass can alter the intensity and the seedlings may stretch and become ‘leggy.’ (There are many good plumeria seed germination methods, I suggest you research each one and use the one or ones that fit you situation.)

When preparing to germinate seeds indoors it is a good idea to soak the seeds overnight or at least 4 hours in a warm place. Also moistening the growing medium before planting any seeds. This will help to ensure that the medium is not over saturated or water logged and that the moisture is spread evenly throughout. Using a tray, spread the seeds so they have about an inch between each, this will help minimize the root damage when transplanting. I have found using plugs is much easier to handle and preserves the roots when transplanting. There are many good planting methods and you should examine each to see which fits your situation and may help result in higher germination rates. If planting is occurring in a flat starting tray, space seeds at least an inch apart, either in rows or in a grid pattern and cover lightly with 1/4″ of growing medium (remember oxygen is important during germination, so don’t pack the medium down to much). Then, spray the entire tray lightly with a hand held mister. The soil should be kept moist not wet long enough for the seeds to germinate, it may need to be sprayed with the mister occasionally to maintain even distribution of moisture. Some growers use starting trays that have plastic, hood-type lids. This will keep the humidity around the seeds at higher than average room levels and may help increase the chance of successful germination. Be sure to check the seeds daily to maintain an optimal environment.

Environmental Considerations

As the plumeria seedlings begin to pop up through the soil, there are a few environmental aspects that should be given proper attention right away: light intensity, humidity, and air flow. Remember the seeds of different cultivars may germinate in different lengths of time. Usually plumeria seeds will germinate in 5-10 days, but I have seen it take up to 30 days if conditions aren’t right. Plumeria seeds can sprout in total darkness, but, once the seedling breaches the soil, a sufficient light source is imperative. Those first “true leafs” will need a light source to perform photosynthesis and create carbohydrates, which will help sustain both normal plant growth and, most importantly, root growth. Without proper lighting, the early vegetative growth of a plant can be negatively affected and could cause long lasting problems.

Humidity can be helpful during the initial germination process but, as the seedlings begin to grow, high levels of humidity can spell disaster. As internal process burn up the seedlings energy sources, the plants will need to release oxygen as a gas through their stomata (a process called transpiration). As the oxygen leaves the plant, water and elemental nutrients are pulled up through the roots. In a humid environment, the stomata will remain closed and the roots will not take in water. If the growing medium is wet without proper aeration, the water will have nowhere to go and the roots will likely suffocate and die.

Air flow and humidity almost go hand in hand. A nice flow of air through the plants canopy will encourage the flow of carbon dioxide to the leaves and, subsequently, oxygen away from them. This is not just true for seedlings, but for plants in all stages of growth. A small fan on medium or low can help keep humidity levels low and the heat from any supplemental lighting to a minimum. Be sure to keep the rooting medium moist, but not too wet. Seedlings need water and going to long without can result in serious damage. However, if the medium remains too wet for too long it may impair root growth. As the seedlings grow, they will eventually exhaust any nutrient charge that the growing medium had to offer, so light fertilization may be needed while waiting to transplant into a different container.

As the seedlings grow, with proper care and attention, they inch closer and closer to fulfilling their own unique destiny. Every plumeria seeds has it’s own DNA structure and will not be exactly like any other. As we stand by, eagerly awaiting the flowers of our labor, it is important to remember that every plumeria we grow has entered into this life as a small, almost insignificant looking thing, that so many refer to as simply, just a seed.

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Propagation

Plant propagation is the branch of horticulture which deals with the deliberate (or intentional) production of new plants using various starter materials, including their intensive but temporary care. It is primarily practiced to produce seedlings or clones of plants for planting in containers for display or decor or other uses.
To understand the science of why, when, and how to propagate requires basic knowledge of plant growth and development, plant anatomy and morphology, and plant physiology.

Plumeria Propagation Methods

In general, there are two methods of propagating plumeria: sexual and asexual.

Sexual propagation is with the use of seeds that is separated from the parent plumeria. This method is so termed "sexual" because there is the involvement of the sexes, referring to the contribution of both the male and female gametes in the production of new plants.

The propagated plumeria therefore has a genotype which results from combining those which originate from the parental sources of male and female gametes. Consequently, the resulting plumeria may exhibit either, or somewhat different, or a combination of parental characteristics.

The young plumera that is produced from seed is called seedling while clonal seedling or simply clone is used for that which is vegetatively produced. However, seedling is now used as a general term to refer to any young plant without regard to the method of propagation.

It does not mean, however, that all plumeria which are propagated by seed are sexually reproduced. Plumeria can produce apomictic seeds. Apomixis is the production of seeds without sexual union.

There are several advantages of sexual propagation:

It may result in new cultivars and vigorous hybrids.
It provides a way to avoid transmission of particular diseases, such as viruses.
It maintains genetic variation, which increases the potential for plants to adapt to environmental pressures.

Asexual propagation, also called vegetative propagation, is with the use of planting materials which are vegetative parts of any plant rather than seeds or spores which are reproductive parts. In most techniques, the propagule is separated first from the parent plumeria and treated to induce regeneration or otherwise directly planted.

Tissue culture, also called in vitro culture and micropropagation, is the technique of propagating plants indoor under aseptic or sterile conditions in artificial growth media. The growth medium, also called nutrient solution, is a mixture of essential elements. The initial propagule in tissue culture is called explant.

Sexual Propagation

Sexual propagation is the reproduction of plants by seeds. The genetic material of two parents is combined by pollination and fertilization to create offspring that are different from each parent.

Seeds

A seed is composed of three major parts: embryo, nutritive (food storage) tissue, and protective tissue. The embryo is a miniature plant in a resting (dormant) state. Plumeria seeds contain a built-in food supply called the endosperm. The protective outer covering of a seed is called the seed coat. It protects seeds from mechanical injury and from diseases and insects. Also, the seed coat usually prevents water from entering the seed until time to germinate. The seed coat allows seeds to be stored for extended periods. The seed leaves, cotyledons, differ in shape from the true leaves. Plumeria are dicots and produce two cotyledons.

To obtain vigorous plumeria from seeds, start with high-quality seeds from a reliable source. Select cultivars that have a chance of providing the desired size, color, and growth habit. Choose cultivars already adapted to your area. Some cultivars are hybrids and may cost more than open-pollinated types, but they usually have a better chance of producing the desired characteristics than non-hybrids.

Purchase only enough seeds for one year because the likelihood of germination decreases with age. Plumeria seeds have been know to germinate after 10 years, but only 10% of the test group germinated. The seed packet label usually indicates essential information about the cultivar or species, such as the year in which the seeds were packaged, the germination percentage, and whether the seeds have received any chemical treatment.

If seeds are obtained well ahead of the actual sowing date (or are surplus seeds), store them in a cool, dry place. Laminated or foil packages help ensure dry storage. Paper packets are best kept in tightly sealed containers and maintained around 40°F in low humidity. A good storage location would be an airtight jar. Collectors can save money and cultivate a rewarding hobby by saving seeds from plumeria in their own gardens. Seeds that have been produced through insect, animal or wind, or other natural pollination methods are known as open-pollinated. Open-pollination can increase biodiversity, and plumeria will almost always display different characteristics than the parent plants. This is especially true when saving seed from hybrids.

Germination

Germination is the resumption of active embryo growth after a dormant period. Three conditions must be satisfied for a seed to germinate:

The seed must be viable; that is, the embryo must be alive and capable of germination.
Internal conditions of the seed must be favorable for germination; that is, any physical, chemical, or physiological barriers to germination must have disappeared or must have been removed by the propagator.
The seed must be subjected to appropriate environmental conditions, including water (moisture), proper temperature and oxygen.

The first step in germination is absorption of water. An adequate, continuous supply of moisture is important to ensure germination. Once germination has begun, a dry period can kill the embryo.

Plumeria germinate in either light or dark. Respiration in dormant seeds is low, but they do require some oxygen. Respiration rate increases during germination. The medium in which the seeds are sown should be loose and well aerated. If the oxygen supply during germination is limited or reduced, germination can be severely retarded or inhibited.

Temperature affects the germination percentage and the rate (speed) of germination. Plumeria seeds have a minimum germination of 50°F, a maximum of around 95°F, and an optimum germination temperature of 80°F. The optimum temperatures for most plumeria is 75 to 85°F.

Seed Dormancy

Viable seeds that do not germinate are dormant. Dormancy can be regulated by the environment or by the seed itself. If a seed is not exposed to sufficient moisture, proper temperature or oxygen the seed will not germinate. In this case, the seed’s dormancy is caused by unfavorable environmental conditions.

Some seeds may not germinate because of some inhibitory factor of the seed itself. This kind of dormancy consists of two general types: (a) seed coat (or external) dormancy and (b) internal (endogenous) dormancy. A seed can also exhibit both kinds of dormancy.

Growing Plumeria from Seeds

Media

A wide range of media can be used to germinate seeds. With experience, you will learn to determine what works best for you. The germinating medium should be fine and uniform yet well aerated and loose. It should be free of insects, disease organisms, nematodes, weeds, and weed seeds. It should also be of low fertility and capable of holding moisture but be well drained. Purchase commercial seed growing media containing fine-particle pine bark, sphagnum peat moss, and perlite, or prepare a combination of equal parts (by volume) of these materials. Do not use garden (mineral) soil to start seedlings; it is not sterile, it is too heavy, and it does not drain well. Soil mixes have little fertility, so seedlings should be watered with a dilute fertilizer solution soon after germination and emergence.

Containers

Plastic cell packs can be purchased or reused if sterilized. In most systems, each cell holds a single plant. This method reduces the risk of root injury when transplanting. Peat pellets, peat pots, or expanded foam cubes can also be used for producing seedlings. Resourceful gardeners often use cottage cheese containers, the bottoms of milk cartons, bleach containers, or plastic cups. Just make certain that adequate drainage holes are made in the bottoms of the containers and that the containers are sterile.

Sterilizing Containers

The importance of using sterile medium and containers cannot be overemphasized. Before using the containers, wash them to remove any debris, immerse them in a fresh solution of one part chlorine bleach to nine parts water for five minutes, and allow them to dry.

Starting Seeds

Seedlings are often started indoors often using heated grow mats. A common mistake is to sow the seeds too early and then attempt to hold the seedlings under poor environmental conditions. This usually results in tall, weak, spindly plants that do not perform well in the garden. The following paragraphs give general guidelines for sowing seeds for transplants.

When sowing plumeria seeds, fill the container to within ³⁄₄-inch of the top with moistened growing medium.

Plumeria Seedlings in individual containers are easier to label and handle at transplanting time than those that have resulted from broadcasting. Place the seed with the fan up and the bulk part of the seed almost all the way in the soil leaving the fan sticking out of the soil. Sow the seeds with the fan pointing up or by uniformly spreading the seeds over a tray filled with soil. Cover the seeds lightly; a suitable planting depth is usually about 1/4 inch of soil over the seeds.

Plumeria seeds are frequently sown directly in a small container or cell pack, which eliminates the need for early transplanting. Usually, one seeds per cell.

Most garden stores and seed catalogs offer indoor or outdoor grow mats. Grow mats have a precisely controlled temperature. Grow mats allow uniform emergence, eliminate overcrowding, and permit sowing indoor and before warm weather.

Water and Light

Moisten the planting medium thoroughly before planting. After seeding, spray with a fine mist or place the containers in a pan or tray that contains about 1 inch of warm water. When the planting mix is saturated, set the container aside to drain. The soil should be moist but not overly wet.

The seed flats should remain sufficiently moist during the germination period. Excessive moisture, however, can lead to damping-off or other disease or insect problems. Place the whole flat or pot into a clear plastic bag to maintain moisture. The plastic should be at least 1 inch above the soil. Keep the container out of direct sunlight; otherwise, the temperature may increase and injure the seeds. Be sure to remove the plastic bag or glass cover when the first seedlings emerge.

After the seeds have germinated, move the flats to a sunny location; the temperature should be over 75°F during the day and a minimum of 60°F at night. This prevents soft, leggy growth and minimizes disease problems. Some, of course, will grow at different temperatures.

Indoors, seedlings must receive bright light after germination. Place them in a south-facing window. If a large, bright location is not available, place the seedlings under fluorescent lights. Use two 40-watt, cool-white fluorescent tubes or special plant growth lamps. Position the plants 6 inches below the light source and provide 16 hours of light daily. As the seedlings grow, the lights should be raised.

Transplanting Seedlings

Plumeria seeds not seeded individually must eventually be transplanted into their own containers as seedlings to give them proper growing space. A common mistake is to leave the seedlings in the flat or common container too long. The ideal time to transplant young seedlings is when the first true leaves appear.

For grouped seedlings, dig up the small plants carefully with a knife or plant label. Let the group of seedlings fall apart and pick out individual plants. Gently ease them apart to avoid root injury in the process. Handle small seedlings by their leaves, not their delicate stems. Using a small tool or your finger, punch a hole in the medium. Plant a seedling at the same depth at which it was growing in the seed flat. Firm the soil and water gently. Keep newly transplanted seedlings in the shade for a few days, or place them under fluorescent lights. Locate them away from sources of direct heat. Continue watering and fertilizing as in the seed flats.

Containers for seedlings should be economical, durable, and make efficient use of available space. Individual pots or plastic cell packs can be used. Another possibility is compressed peat or coir plugs, which expand to form compact individual pots when soaked in water. They waste no space, do not fall apart as easily as peat pots, and can be set out directly in the next size pot when time to transplant. If you wish to avoid transplanting seedlings altogether, compressed peat or coir pellets are excellent for direct sowing.

When setting plants outdoors that were grown in peat or coir pots, be sure to break the mesh on the sides of the pot and to cover the pot completely with growing media. If the top edge of the peat pot extends above the soil level, it may act as a wick and draw water away from the soil in the pot. Tear off the top lip of the pot and plant below the soil surface.

The three parts to a seed:

The protective tissue or seed coat
The embryo which grows into a new plant.
The endosperm which is the nutritive or food storage supplying nutrients to the embryo.

Asexual Propagation Cuttings

Asexual propagation is the process of taking vegetative pieces of a desirable plant and reproducing new plants from these tissues. Asexual propagation permits cloning of plants, meaning the resulting plants are genetically identical to the parent plant. The major methods of asexual propagation are cuttings, layering, division, separation, budding, grafting, and micropropagation (tissue culture).

CUTTINGS

Propagation by cuttings involves rooting a severed piece of the parent plant or, in some cases, producing new plants from severed pieces of tissue (leaf cuttings). A greenhouse is not necessary for successful propagation by cuttings. Cutting are best propagated at the beginning of the growing season.

If rooting only a few cuttings, you can use a flowerpot. Maintain high humidity by covering the pot with a bottomless milk jug or by placing the pot into a clear plastic bag. Cuttings can also be placed in plastic trays covered with clear plastic stretched over a wire frame.

Containers must have holes in the bottoms for drainage. The plastic helps keep the humidity high and reduces water loss from the plant. If a more elaborate structure is needed, construct a small hoop frame or use an intermittent mist system. Horticulture Information Leaflet, A Small Backyard Greenhouse for the Home Gardener, may be helpful.

The rooting medium should be sterile, low in fertility and well drained to provide sufficient aeration. Materials commonly used are coarse sand, a mixture of one part peat and one or two parts perlite (by volume), or one part peat and one part sand (by volume). Various commercial potting media may also be used. Vermiculite by itself is not recommended because it packs and tends to hold too much moisture.

There are several different kinds of cuttings. Which type you use depends on the growing habit of the plant and, often, the plant’s growth stage. The vast majority of cuttings are tip cutting, but center cutting are also use.

Types of Rooting Media

Peat moss consists of the remains of aquatic, marsh, or bog vegetation that have been preserved under water in a partially decomposed state. Peat bogs are vital ecosystems. They provide unique habitats for wetland plants and animals, actively absorb runoff and prevent erosion, filter contaminants out of water, and are the largest carbon sinks on earth. Peat moss has been harvested for fuel as well as horticultural use for many years. Unfortunately, it is regenerated at extremely slow rates and harvesting this resource is not considered sustainable. Several environmentally friendly alternatives to peat moss include composted bark, coconut coir, brewing waste, and pulp and paper sludge. There are different types of peat moss, some more suitable than others. Sphagnum peat moss is recommended because it tends to be acidic, with a pH ranging from 4.0 to 5.0, and because it usually has very low fertility. Materials such as Michigan peat, peat humus, and native peat are usually too decomposed to provide satisfactory structure and drainage. Peat moss should be broken apart and moistened before use.

Coir pith is also known as Coco peat or Coir dust. This by-product of the coir industry can be converted into organic manure using biotechnology, making it ideal for gardening and horticulture. A wide variety of Coir pith products such as Coir pith grow bag, Coir pith bale, Coir pith Briquettes, Coir pith Discs, and Coco chips are ideal for your gardening and horticultural needs. Coirpith not only revitalizes your plants, it induces uniformity in growth by enhancing water retention and microbial activity. Coir pith contains high quality of nutrients that keep the soil healthy in a natural way. It acts as a top dressing that helps maintain moisture and reconditions the soil. Coir pith enhances the nutrient carrying capacity of plants. Sustainable agriculture practices such as this creates a healthy perfect loop from table to earth. Pure and natural, this organic biodegradable matter is an economical and natural alternate for rockwool slabs, peatmoss and perlite.

Vermiculite is a sterile, lightweight medium produced by heating a type of clay to 2000°F. Vermiculite holds large quantities of air, water, and nutrients. The pH usually ranges from 6.5 to 7.2. Vermiculite is available in four particle sizes. Use the larger-sized particles because they provide better soil aeration. For horticultural mixes, sizes 2 or 3 are generally used.

Perlite is produced from a type of volcanic rock that is crushed, screened, and then heated to approximately 1400°F. The result is a very lightweight, porous material. Its principal value in propagation mixtures is aeration. It does not hold water and nutrients as well as vermiculite. The pH ranges from 7.0 to 7.5. Sometimes perlite can cause fluoride burn, usually on the leaf tips of some foliage plants.

Sand consists of small, weathered rock particles, usually silicaceous in origin. It is heavy and has no nutrient value. Sand occurs in different grades; sharp builders’ sand is best for propagation. Fine sands are not recommended. Sterilize sand before using it; sand may contain various disease pathogens, weeds, and weed seeds.

Bark, partially decomposed pine bark, is often used as a rooting medium. Milled pine bark is lightweight, has a pH of 5.8 to 6.0, and is capable of holding nutrients while providing excellent drainage and aeration.

Leaf-Bud Cuttings

Leaf-bud cuttings are used when space or cutting material is limited. Each node on a stem can be treated as a cutting. The cutting consists of a leaf blade, petiole, and a short piece of stem with an attached axillary bud. Place cuttings in the medium with the bud covered (to 1 inch) and the leaf exposed. A modified version of a leaf-bud cutting, referred to as a single node cutting, can be prepared simply by cutting the stem below and above the leaf petiole having a well-developed axillary bud. Examples of plants propagated this way include blackberry, camellia, clematis, devil’s ivy, dracaena, grape ivy, heart-leaf philodendron, jade plant, mahonia, rhododendron, and rubber plant.

Center Cuttings

A center cutting is an easy way to propagate some overgrown, leggy plumeria. Leafless stem sections (12 to 18 inches long) are cut from older stems. Each center cut should contain multiple leaf nodes. Insert the cutting vertically with about 3" of the cutting below the surface of the medium, and leave a bud facing upward. Center cuttings are usually potted when roots and new shoots appear.

Tip Cuttings

Propagation by stem cuttings is the most commonly used method for plumeria plants. Typically, tip cuttings of some cultivars and varities are more difficult to root successfully; however, cuttings from almost all plumeria trees can be rooted.

Types of Stem Cuttings

The four main types of stem cuttings are herbaceous, softwood, semi-hardwood, and hardwood. These terms reflect the growth stage of the stock plant, which is one of the most important factors influencing whether cuttings produce roots. Calendar dates are useful only as guidelines. Refer to Table 13–2 for more information on optimum growth stages for rooting stem cuttings of various woody ornamentals.

Softwood cuttings are prepared from soft, succulent, new growth of woody plants, just as it begins to harden (mature). It is believed by many this type of cutting is best for grafting. Shoots are suitable for making softwood cuttings when they still have a gradation of leaf size (oldest leaves are mature whereas newest leaves are still small). This stage typically occurs in May, June, or July. The soft shoots are quite tender, and extra care must be taken to keep them from drying out and are not considered good for rooting and have a greater tendency to root.
Semi-hardwood cuttings are usually prepared from partially mature wood of the current season’s growth, just after a flush of growth. This type of cutting normally is made from mid-June to late summer. The wood is reasonably firm and the leaves of mature size.
Hardwood cuttings are taken from mature stems from the previous years growth in late winter or early spring. Plants are generally just coming out of dormancy with some obvious signs of active growth. The wood is firm and does not bend easily. Hardwood cuttings are most often used for rooting. A straight single tip cutting is the most commonly used stem cutting.

Procedures for Rooting Woody Stem Cuttings

Cuttings should generally consist of the current or past season’s growth. Avoid material with flower buds. Remove any flowers and flower buds when preparing cuttings so the cuttings’ energy can be used in producing new roots rather than flowers. Take cuttings from healthy, disease-free plants.

The fertility status of the stock (parent) plant can influence rooting. Avoid taking cuttings from plants that show symptoms of nutrient deficiency. Conversely, plants that have been fertilized heavily, particularly with nitrogen, also may not root well. The stock plant should not be under water stress. In general, cuttings taken from young plants root quicker than cuttings taken from older, more mature plants. Cuttings from lateral shoots often root better than cuttings from terminal shoots.

Early morning is the best time to take cuttings because the plant is fully turgid. It is important to keep the cuttings cool and moist until they are stuck. An ice chest or a dark plastic bag with wet paper towels may be used to store cuttings. If there will be a delay in sticking cuttings, store them in a plastic bag in a refrigerator.

While terminal bud ends of the stem are best, a long shoot can be divided into several cuttings. Cuttings are generally 4 to 6 inches long. Use a sharp, thin bladed pocketknife or sharp pruning shears. Dip the cutting tool in rubbing alcohol or a mixture of one part bleach to nine parts water to prevent transmitting diseases from infected plant parts to healthy ones.

Remove the leaves on the lower one-third to one-half of the cutting. On large-leafed plants, the remaining leaves may be cut in half perpendicular to the mid vein to reduce moisture loss and conserve space in the rooting area.

During preparation of stem cuttings of particular woody species, the lower portion of the stem that is inserted into the rooting media is deliberately wounded, which is done to stimulate rooting. Most species do not require wounding, but some benefit greatly from this practice.

There are two general types of wounds, light and heavy. A light wound consists of two or four equidistant vertical cuts, administered with a knife or single-edge razor blade, to the lower portion (approximately 1 to 1½-inches) of the cutting. The cuts go through the bark into the wood but are not deep enough to split the stem. Many conifer cuttings respond to light wounds. On the other hand, a heavy wound consists of removal of a thin strip of bark on one or opposite sides of the lower 1 to 1½-inches of a cutting, exposing the green tissue just beneath the bark termed the cambium. Be careful when applying a heavy wound not to remove (scrape) all the bark from the lower portion of the stem as this kills the cutting or prevents it from rooting. Species that respond to heavy wounding include magnolias and evergreen rhododendrons. As mentioned previously, most species do not require wounding. There is nothing wrong, however, with using wounding, whether it be light or heavy, on all species provided it is done properly. Also, wounding by itself is of no benefit unless cuttings are treated with root-promoting compounds after wounding.

Treating cuttings with root-promoting compounds (chemicals), particularly for difficult-to-root species, is a common practice when rooting woody stem cuttings because these compounds increase the percentage of cuttings that form roots, speed up the rooting process (make the cuttings root faster), increase the uniformity of rooting, and lastly increase the number and quality of roots produced per cutting. Root-promoting compounds are generally available commercially in two forms, powders or liquids.

When treating cuttings with root-promoting compounds, prevent possible contamination of the entire supply (stock) of formulation by putting some in a separate container before treating cuttings. Any material remaining after treatment should be discarded and not returned to the original container. Be sure to tap the lower portion of the cutting to remove excess material when using a powder formulation. If the base of the cutting is not moist, moisten it with water before applying a powder formulation so the powder adheres to the base. Once the cuttings have been treated with a powder formulation, use a dibble for inserting them into the rooting medium so the powder stays on during insertion. When treating cuttings with a liquid formulation of a root-promoting compound, dip the lower ½-inch to 2 inches of a cutting into the solution for 1 to 2 seconds followed by 15 to 20 minutes of air drying; then insert the cutting into the rooting medium without the use of a dibble.

Use a rooting medium such as coarse sand, pine bark, or a mixture of one part peat and one or two parts perlite (by volume), or peat and sand (1:1 by volume). The rooting medium should be sterile, low in fertility, sufficiently well drained to permit aeration, and moisture retentive enough so that it does not have to be watered too frequently. Moisten the medium before inserting cuttings. Various commercial potting mixes can be used. Insert the cuttings one-third to one-half of their length into the medium with the buds pointing upward. Do not insert the stem upside down. Space cuttings just far enough apart to allow all leaves to receive sunlight. Water again after inserting the cuttings if the containers or frames are 3 or more inches deep. Cover the cuttings with plastic and place in indirect light. Keep the medium moist until the cuttings have rooted. Rooting is improved if the plants are misted on a regular basis.

Rooting time varies with the type of cutting, the species being rooted, and environmental conditions. Conifers require more time than broadleaf plants. Late fall or early winter is a good time to root conifers. Once rooted, conifer cuttings may be left in the rooting structure until spring.

Figure 13–7. Remove the petiole, cut the veins, and then lay the leaf of a rex begonia flat on the medium surface. A new plant will grow from each cut vein.

Figure 13–8. Many plants can be propagated by leaf-bud cuttings.

Asexual Propagation – Other Methods

LAYERING

Stems still attached to their parent plant may form roots where they come in contact with a rooting medium. This method of vegetative propagation is generally successful because water stress is minimized and carbohydrate and mineral nutrient levels are high. The development of roots on a stem while the stem is still attached to the parent plant is called layering. A layer is a rooted stem after it has been removed from the parent plant. Some plants propagate naturally by layering, but sometimes plant propagators assist the process. Layering is enhanced by wounding one side of the stem where the roots are to form or by bending it very sharply. The rooting medium should always provide aeration and a constant supply of moisture. Some common forms of layering are as follows. However, keep in mind these protocols are sometimes modified.

Air layering (pot layering, circumposition, marcottage, Chinese layering, gootee). Air layering can be used to propagate large, overgrown houseplants (such as rubber plants or dieffenbachia that have lost most of their lower leaves) as well as some woody ornamentals such as camellias. The process varies depending on whether the plant is a monocot or dicot. For monocots, such as Dracaena fragrans ‘Massangeana’ (corn plant), make an upward cut about one-third of the way through the stem. This is normally done on a stem about 1 foot from the tip. The cut is held open with a toothpick or wooden matchstick Surround the wound with damp, unmilled sphagnum moss. Wrap the moss with plastic and hold in place with twist ties or electrician’s tape. Aluminum foil can also be used; it does not require twist ties or tape to hold it in place.

The process for dicots is similar except a 1-inch ring of bark is removed from the stem. Scrape the newly bared ring to remove the cambial tissue in order to prevent callus from forming. Wrap and cover using the same procedure as that described for monocots.

After the rooting medium is filled with roots, sever the stem below the medium. The new plant requires some pampering after planting until the root system becomes more developed.

Natural forms of layering – Sometimes layering happens without the help of a propagator. Runners and offsets are specialized structures that facilitate propagation by layering.

A runner produces new shoots where it touches the growing medium. Plants that produce stolons or runners are propagated by severing the new plants from their parent stems. Plantlets at the tips of runners may be rooted while still attached to the parent or detached and placed in a rooting medium. Examples include strawberry and spider plants.

Plants with a rosetted stem often reproduce by forming new shoots, called offsets (offshoots), at their base or in the leaf axil. Sever the new shoots from the parent plant after they have developed their own root system. Unrooted offsets of some species may be removed and placed in a rooting medium. Some of these must be cut off, whereas others may simply be lifted from the parent stem. Examples include date palm, haworthia, bromeliads, and many cacti.

SEPARATION AND DIVISION

Separation and division are the easiest and quickest ways to propagate many plants. Separation uses naturally occurring vegetative structures such as bulbs and corms. Individual bulbs or corms are separated from a clump. Most of the spring- and summer flowering bulbs are propagated this way. Division involves digging up the plant or removing it from its container and cutting (dividing) the plant into separate pieces. Division uses specialized vegetative structures such as rhizomes and tubers. Indoor plants that can be propagated by division include ferns, snake plant, prayer plant, and African violet. Outdoor plants that can be divided include many perennials such as daylily, hosta, iris, liriope, and verbena. Separation and division are normally done in the fall or early spring.

BUDDING AND GRAFTING

Budding

Budding and grafting are methods of asexual propagation that join parts of two or more different plants together so they unite and grow as one plant. These techniques are used to propagate cultivars that do not root well from cuttings or to alter some aspect of the plant (for example, to create weeping or dwarf forms).

Most fruit and nut trees are propagated by budding or grafting.

The scion consists of a short stem piece with one or more buds and is the part of the graft that develops into the top of the grafted plant. The rootstock (also called stock or understock) provides the new plant’s root system and sometimes the lower part of the stem. Seedling rootstocks are used commonly.

Six conditions must be met for bud grafting to be successful:

The scion and rootstock must be compatible (capable of uniting).
The scion and stock plant must be at the proper physiological stage of growth.
The cambial region of the scion and the stock must be in close contact—touching if possible.
Proper polarity must be maintained (the buds on the scion must be pointed upward).
Immediately after grafting, all cut surfaces must be protected from drying out.
Proper care must be given to the graft after grafting.

Once the bud has healed and broken to form a shoot, the top of the stock plant is cut back (removed) to the bud union.

Not all plants can be grafted. The two plants should be closely related taxonomically. Grafting between clones and seedlings of the same species is usually successful.

Budding, or bud grafting, is the union of one bud, with or without a small piece of bark, from one plant (scion) onto a stem of a rootstock. It is especially useful when scion material is limited. Budding is usually done during the growing season when the bark is slipping (soft and easy to peel back from the cambium), June through August in the Southeast U.S., but it can also be done in late winter or early spring.

T-budding—This is the most commonly used budding technique. When the bark is slipping, make a vertical cut (same axis as the rootstock) through the bark of the rootstock, avoiding any buds on the stock. Make an intersecting, horizontal cut at the top of the vertical cut (forming a “T” shape), and loosen the bark by twisting the knife slightly at the intersection. Remove a shield shaped piece of the scion, including a bud, some bark, and a thin section of wood. Push the shield under the loosened stock bark at the "T". Wrap the union, leaving the bud exposed. Many fruit trees are propagated by this method.

Chip budding—This method can be used when the bark is not slipping. Although all the basics in handling budwood and stock are the same for chip budding and T-budding, the cuts made in chip budding differ radically. The first cut on both stock and scion is made at a 45^o to 60^o downward angle to a depth of about ⅛-inch. After making this cut on a smooth part of the rootstock, start the second cut about ¾-inch higher and draw the knife down to meet the first cut. (The exact spacing between the cuts varies with species and the size of the buds.) Then remove the chip. Cuts on both the scion (to remove the bud) and the rootstock (to insert the bud) should be exactly the same size. Although the exact location is not essential, the bud is usually positioned one-third of the way down from the beginning of the cut. If the bud shield is significantly narrower than the rootstock cut, line up one side exactly. Wrapping is extremely important in chip budding. If all exposed edges of the cut are not covered, the bud dries out before it can “take.” Chip budding has become more popular over the past five years because of the availability of thin (2 mil) polyethylene tape as a wrapping material. This tape is wrapped to overlap all of the injury, including the bud, and forms a miniature plastic greenhouse over the healing graft.

Grafting

Grafting is the union of the stems of two plants to grow as one. There are several kinds of grafting; which method to use depends on the age and type of plants involved.

Whip or tongue grafting—This method is often used for stems ¼-inch to ½-inch in diameter. The scion and rootstock are usually of the same diameter. This graft provides excellent cambial contact and heals quickly. Make a sloping cut 1-inch to 2½-inches long at the top of the rootstock and a matching cut on the bottom of the scion. On the cut surface, slice downward into the stock and up into the scion, so the pieces will interlock when brought together. Fit the pieces together such that the cambium matches on at least one side, and then wrap and tie or wax the graft union.

Cleft grafting—Cleft grafting is one of oldest and most widely used methods of grafting. The two most common circumstances when one would use this technique are (1) when creating a weeping ornamental tree and (2) when upgrading an older cultivar of a fruit tree to a newer, improved one while maintaining the existing root system. Cleft grafting is best done in early spring when the buds on the stock plant are beginning to swell but before active growth has begun. The scions, however, must be fully dormant. Collect scion wood ⅜ to ⅝ -inch in diameter during the dormant season and refrigerate until needed.

Cut the limbs to be reworked at a right angle to the main axis of the branch. Use a heavy knife to split the branch, making a 2-inch vertical cut through the center of the stub to be grafted. Be careful not to tear the bark. Keep this cut wedged apart. Prepare two scion pieces 3 to 5 inches long; cut the lower end of each scion piece into a wedge. Insert the scions at the outer edges of the cut in the stock. Tilt the top of the scion slightly outward and the bottom slightly inward to be sure the cambial layers of the scion and stock touch. Remove the wedge propping the slit open, and cover all cut surfaces with grafting wax. If both scions grow, one can be removed later.

Some other types of grafting include splice, side, stub, side veneer, and side tongue. Check reference books for additional information. Each method has advantages for special situations.

Care of grafts—Grafting is not likely to be successful unless you properly care for the grafted plants for a year or two after grafting. If you use binding materials such as waxed string or nursery tape on the graft, remove them shortly after growth starts to prevent girdling. Rubber budding strips have some advantages over other materials. They expand with growth and usually do not need to be removed because they deteriorate after several months. Inspect the grafts after two or three weeks to see if the grafting wax has cracked and, if necessary, rewax the exposed surface. After this, the union will probably have healed and no more waxing will be necessary.

Limbs on the old cultivar (rootstock) that are not selected for grafting should be cut back at the time of grafting. The total leaf surface of the old cultivar should be reduced gradually as the new one increases for one or two years; by this time, the new cultivar (scion) has had adequate time to grow. Completely removing all the limbs of the old cultivar at the time of grafting increases the shock to the tree and causes excessive suckering. Also, the scions may grow too fast, making them susceptible to wind damage.

MICRO PROPAGATION

Micro propagation involves the application of tissue culture techniques to propagate plants from very small plant parts (parts of leaves, stems, shoot tips, root tips, single cells, and pollen grains). The small plant part is grown (cultured) in a test tube, petri dish, or other sterilized container with a culture medium and precise environmental conditions. The container and growing medium must be sterilized. Because plants often harbor bacterial and fungal spores, the plant tissue must also be disinfected.

Micro propagation is a rapidly growing part of the plant propagation industry. It is not practical for most home gardeners because of the very specific requirements of the culture media and the constant efforts that must be made to avoid possible contamination from disease organisms. For nurseries, special care must be taken in transporting micro propagated plants from the lab to the store because they are not acclimated to outdoor growing conditions.

Hardening Plants

Hardening is the process of conditioning a plant for growth outdoors. If plants produced inside are planted outdoors without a hardening period, their growth could be severely limited. Hardening is most critical with early crops, when adverse climatic conditions can be expected.

Hardening is accomplished by decreasing temperature and relative humidity gradually, and reducing water. This procedure results in accumulation of carbohydrates and thickening of cell walls. A change from a soft, succulent type of growth to a firmer, harder type is desired.

The process should be started at least two weeks before plants are to be planted in the garden. Place seedlings outside in a protected area on warm days. Increase the length of exposure gradually. Do not put tender seedlings outdoors on windy days or when temperatures are below 45°F. Even cold-hardy plants will be injured if exposed to freezing temperatures before they are hardened.

The hardening process is intended to slow plant growth. Carried to an extreme, however, hardening can cause significant damage. For example, cauliflower produces thumb-sized heads and fail to develop further if hardened too severely; cucumbers and melons stop growing entirely.

Related Images:

What food do seeds need?

A typical seed has the following parts and the functions.

Radicle = It is embryonic root system.during seed germination it begins to grow and goes down in the soil to form the root system.
Plumule = It is the embryonic shoot system. During germination it begins to grow and form the shoot system; viz. stem,branches and leaves.
Cotyledon/s = These are the godowns of reserve food that is required during germination. The stored food is largely in the form of starch, proteins and oils.
All the pulses i.e. peas and beans are good examples of this; and that is precisely why they are cultivated by mankind.
Endosperm = This is also a godown of reserve food for the same purpose mentioned above. It is mostly found in the cereals like rice,wheat, maize,oats and barley,and that is precisely why these are cultivated.Thus, a seed gets stored food for its growth from cotyledons or endosperm; but both these parts are never functional simultaneously. In those plants where the cotyledons store reserve food, the endosperm is non-existent,examples are all the pulses (see above)

When the endosperm stores reserve food , the cotyledons are non-functional,examples are all cereals (see above).In short both of them are never functional in the same plant.

The reserve food is just sufficient to let the seedling become independent. When the first green leaves appear it no longer requires the food from the godown.

The seed of a higher plant is a small package produced in a flower or cone containing an embryo and stored food reserves. Germination and early seedling growth require the mobilization of food storage reserves within the seed. A major portion of almost every seed consists of food reserves. Angiosperms fall into two groups regarding the placement of stored food in their seeds: the monocots which store most of their food in the cotyledons or seed leaves; and the dicots which store their food in extraembryonic tissues called endosperm (Gottfried, 1993).

Under favorable conditions, the seed begins to germinate, and the embryonic tissues resume growth, developing towards a seedling. The first step in germination of a seed occurs when it imbibes, or takes up water. Once this has taken place, metabolism within the embryo resumes (Gottfried, 1993). The part of the plant that emerges from the seed first is termed a radicle or young root—which anchors the seed and absorbs water and minerals from the soil (Gottfried, 1993). In some definitions, the appearance of the radicle marks the end of germination and the beginning of "establishment", a period that ends when the seedling has exhausted the food reserves stored in the seed. Then, the shoot of the young seedling elongates and emerges from the ground. These are critical phases in the life of a plant. The mortality between dispersal of seeds and completion of establishment can be so high, that many species survive only by producing huge numbers of seeds (wikipedia.org, 2006).

Seed germination depends on a variety of environmental factors, the most important of which is water. However, other factors such as the availability of oxygen (for aerobic respiration in the germinating seed), suitable temperature, and sometimes the presence of light are also necessary (Gottfried, 1993).