Sexual propagation-Plant propagation - Wikipedia

Log In. Plant propagation is the process of producing a new plant from an existing one. It is both art and science requiring knowledge, skill, manual dexterity, and experience for success. 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. There are two general types of propagation: sexual and asexual.

Sexual propagation

Sexual propagation

Sexual propagation

Sexual propagation

This is especially true when saving seed from hybrids. These and Sexual propagation succulent cuttings will rot if kept too moist. Propagation is not likely to be successful unless you properly care for the plants for a year or two after budding or grafting. It does not hold water and nutrients as well as vermiculite. Sowing in rows propagahion Sexual propagation and air movement.

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These include calendula, prolagation, annual phlox, and verbena. Tip layering. If plants produced inside are planted outdoors without a hardening period, their growth could SSexual severely limited. When starting seed in the home, Sexual propagation light can be provided by fluorescent fixtures suspended 6 to 12 inches above the seeds for 16 hours Scout rope machine day. Where germination temperatures are listed, they are usually the optimum temperatures unless otherwise specified. Vegetative propagation. Double Eye: This is used for plants with opposite leaves when space or stock material is limited. The rootstock also called stock or understock provides the new plant's root system and sometimes Sexual propagation lower part of the stem. Peat bogs are vital ecosystems. Vinegar is safer and can be used for some species; the technique is the same as with sulfuric acid. Pregermination Another method of starting seeds is pregermination. Numerous houseplants can be propagated by cane Sexual propagation. This treatment should prevent damping-off and Sexual propagation plant diseases, as well as eliminate potential plant pests.

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  • Edited and revised by David C.
  • Log In.
  • Plant propagation is the branch of horticulture which deals with the deliberate or intentional production of new plants using various starter materials e.
  • Plant propagation is the process in growing new plants from a variety of sources: seeds , cuttings , and other plant parts.

Propagation , in horticulture , the reproduction of plants by any number of natural or artificial means. Many types of seeds may be sown in open ground and, barring extreme wetness or extreme aridity, germinate well enough for practical purposes.

Because many soils harbour fungi destructive to sprouting seed and young seedlings, soil that is used for germinating seed commonly is sterilized by heat or chemicals. Many diseases of plants are caused by fungi and bacteria carried in or on the seed itself, and treatment of the seed with disinfectants is beneficial.

Some species of plants, in their cultivated forms, do not produce seed— e. In a great number of cultivated species, seedlings vary so much that the desired traits are found in only a small proportion. For these and other reasons, horticulturists resort to asexual propagation— i. Many people have held the opinion that asexual propagation is unnatural and that plants thus derived lack the hardiness or the sturdiness of plants grown from seed.

Asexual propagation, however, is not unnatural; some of its forms— e. Methods of asexual propagation include bulb division, layering, cutting , and grafting. Bulbs and other underground rootlike structures, such as tubers and corms, may be divided as they mature.

The sections are then placed in a moist medium to root. In layering , the stem of a large plant is notched and wrapped in moist sphagnum moss or bent to the ground and covered with moist soil; when roots appear, growing out of the moss, the stem is cut below the roots and potted.

Auxins growth hormones are often added to the wounds or soil to stimulate rooting. Stem cuttings are rooted in water or a moist potting medium such as sand, peat moss, or vermiculite. When cutting or layering are not feasible , a bud or twig of one plant is grafted onto the fully developed root system of another.

Info Print Print. Table Of Contents. Submit Feedback. Thank you for your feedback. Introduction Sexual propagation. Asexual propagation. See Article History. Its two objectives are…. Facts Matter. Start Your Free Trial Today. Its two objectives are to achieve an increase in numbers and to preserve the essential characteristics of the plant.

Propagation can be achieved sexually by seed or asexually by utilizing specialized…. New plants are produced either from seed or by the techniques of division, taking cuttings, grafting, budding, or layering. Propagation of crop plants, involving the formation and development of new individuals in the establishment of new plantings, is usually accomplished by the use of either seeds or the vegetative parts of plants.

The first type, known as sexual propagation, is used for asparagus,…. History at your fingertips. Sign up here to see what happened On This Day , every day in your inbox! By signing up, you agree to our Privacy Notice. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.

The rooting medium should always provide aeration and a constant supply of moisture. There could be several reasons your seeds failed to germinate. The container and growing medium must be sterilized. Hartmann, Hudson T. The proper time for sowing seeds for transplants depends upon when plants may safely be moved out-of-doors in your area. Gently pull the bulbs apart and replant them immediately so their roots can begin to develop. Stratification Seeds of some fall-ripening trees and shrubs of the temperate zone will not germinate unless chilled underground as they over winter.

Sexual propagation

Sexual propagation

Sexual propagation

Sexual propagation

Sexual propagation. Publications

Plant propagation methods can also be divided into two types: conventional and modern. Conventional propagation is the usual method of plant multiplication using plant organs, such as seeds and stems, under "outside" or outdoor conditions. Seed propagation is applied in the spermatophytes or seed-bearing plants which include the gymnosperms naked-seed plants and the angiosperms enclosed-seed plants or true-flowering plants.

Plants which are propagated from spore belong to the fern family and allies, including mosses. In plant propagation using the seed or spore as propagation material, fertilization or the union of the male and female gametes is a precondition for the production of new plants. However, there is a difference between the two. In seeds, a miniature plant the embryo within the organ has been predeveloped after undergoing fertilization.

This embryo is the one which grows to form the new plant. This means that fertilization first occurs after pollination , and this leads to seed formation. The seed, having a sexually produced and mature embryo, germinates and gives rise to a seedling. The spore is formed without undergoing fertilization. This organ has both male and female gametes which subsequently unite and give rise to new plants.

Budding is an artificial method of asexual propagation in plants. Describes grafting as an artificial method of asexual or vegetative plant propagation and its other uses including production of multiple trunked trees. Brief discussion of vegetative propagation.

Natural vegetative propagules are listed with crop examples. Author reveals how he creates or enhances bonsai deadwood such as shari and jin by employing the expertise of insect sculptors. Back to Home Page. An enclosed nursery can ensure high relative humidity. Sampagita or Jasminum sambac can be propagated by leaf cuttings. Yellowish parts of leaves were underground. Want to say something?

Place the gel with seedlings in a plastic bag with a hole in it. Squeeze the gel through the hole along a pre-marked garden row. Spacing of seeds is determined by the number of seeds in the gel. The gel will keep the germinating seeds moist until they establish themselves in the garden soil. After the seed has been sown, moisten the planting mix thoroughly.

Use a fine mist or place the containers in a pan or tray which contains about 1 inch of warm water. Avoid splashing or excessive flooding which might displace small seeds. When the planting mix is saturated, set the container aside to drain. The soil should be moist but not wet. Ideally, seed flats should remain sufficiently moist during the germination period without having to add water. One way to maintain moisture is to slip the whole flat or pot into a clear plastic bag after the initial watering.

The plastic should be at least 1 inch from the soil. Keep the container out of direct sunlight; otherwise the temperature may rise to the point where the seeds will be harmed. Many home gardeners cover their flats with panes of glass instead of using a plastic sleeve. Be sure to remove the plastic bag or glass cover as soon as the first seedlings appear.

Surface watering can then be practiced if care and good judgment are used. Lack of uniformity, overwatering, or drying out are problems related to manual watering. Excellent germination and moisture uniformity can be obtained with a low-pressure misting system. Four seconds of mist every 6 minutes or 10 seconds every 15 minutes during the daytime in spring seems to be satisfactory. Bottom heat is an asset with a mist system.

Subirrigation or watering from below may work well, keeping the flats moist. However, as the flats or pots must sit in water constantly, the soil may absorb too much water, and the seeds may rot due to lack of oxygen.

Several factors for good germination have already been mentioned. The last item, and by no means the least important, is temperature. After germination and seedling establishment, move the flats to a light, airy, cooler location, at a 55 to 60 degree F. This will prevent soft, leggy growth and minimize disease troubles. Some crops, of course, may germinate or grow best at a different constant temperature and must be handled separately from the bulk of the plants.

Seedlings must receive bright light after germination. Place them in a window facing south, if possible. If a large, bright window is not available, place the seedlings under a fluorescent light. Use two watt, cool-white fluorescent tubes or special plant growth lamps. Position the plants 6 inches from the tubes and keep the lights on about 16 hours each day.

As the seedlings grow, the lights should be raised. If the plants have not been seeded in individual containers, they must be transplanted to give them proper growing space. The ideal time to transplant young seedlings is when they are small and there is little danger from setback. This is usually about the time the first true leaves appear above or between the cotyledon leaves the cotyledons or seed leaves are the first leaves the seedling produces.

To transplant, carefully dig up the small plants with a knife or wooden plant label. Let the group of seedlings fall apart and pick out individual plants. Handle small seedlings by their leaves, not their delicate stems. Gently ease them apart in small groups which will make it easier to separate individual plants. Avoid tearing roots in the process. Punch a hole in the medium into which the seedling will be planted see below for information about media.

Make it deep enough so the seedling can be put at the same depth it was growing in the seed flat. Small plants or slow growers should be placed 1 inch apart and rapid-growing, large seedlings about 2 inches apart.

After planting, firm the soil and water gently. Keep newly transplanted seedlings in the shade for a few days, or place them under fluorescent lights. Keep them away from direct heat sources. Continue watering and fertilizing as in the seed flats.

These are generally directly seeded outdoors or sown directly into individual containers indoors. Examples include peas, beans, carrots, beets, chard, zinnias and cucurbits, such as melons and squash. Seedling growing mixes and containers can be purchased or prepared similar to those mentioned for germinating seed. Some commercial soilless mixes have fertilizer already added.

Remember that young seedlings are easily damaged by too much fertilizer, especially if they are under any moisture stress. There is a wide variety of containers from which to choose for transplanting seedlings. These containers should be economical, durable, and make good use of space. The type selected will depend on the type of plant to be transplanted and individual growing conditions.

Standard pots may be used, but they waste a great deal of space and may not dry out rapidly enough for the seedling to have sufficient oxygen for proper development. There are many types of containers available commercially. Those made out of pressed peat can be purchased in varying sizes. Individual pots or strips of connected pots fit closely together, are inexpensive, and can be planted directly in the garden.

When setting out plants grown in peat pots, be sure to cover the pot completely. 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. To avoid this, tear off the top lip of the pot and then plant flush with the soil level. Community packs are containers in which there is room to plant several plants. These are generally inexpensive. Compressed peat pellets, when soaked in water, expand to form compact, individual pots.

If you wish to avoid transplanting seedlings altogether, compressed peat pellets are excellent for direct sowing. Community packs and cell packs, which are strips of connected individual pots, are also available in plastic and are frequently used by commercial bedding plant growers, as they withstand frequent handling.

In addition, many homeowners find a variety of materials from around the house useful for containers. These homemade containers should be deep enough to provide adequate soil and have plenty of drainage holes in the bottom. Hardening is the process of altering the quality of plant growth to withstand the change in environmental conditions which occurs when plants are transferred from a greenhouse or home to the garden.

A severe check in growth may occur if plants produced in the home are planted outdoors without a transition period. Hardening can be accomplished by gradually lowering temperatures and relative humidity and reducing water. A change from a soft, succulent type of growth to a firmer, harder type is desired. This process should be started at least 2 weeks before planting in the garden.

If possible, plants should be moved to a 45 to 50 degree F. A cold frame is excellent for this purpose. When put outdoors, plants should be shaded, and then gradually moved into sunlight.

Each day, gradually increase the length of exposure. Even cold-hardy plants will be hurt if exposed to freezing temperatures before they are hardened. After proper hardening, however, they can be planted outdoors and light frosts will not damage them. The hardening process is intended to slow plant growth.

If carried to the extreme of actually stopping plant growth, significant damage can be done to certain crops. For example, cauliflower will make thumb size heads and fail to develop further if hardened too severely. Cucumbers and melons will stop growth if hardened. One tested method for small quantities follows:.

Put a solid, sterilized brick bake at degrees F. When the brick is wet throughout; squeeze a thin layer of moist soil and peat onto the top of the brick. Pack a second layer about an inch on top of that. Sprinkle spores on top. Cover with plastic not touching the spores and put in a warm place in indirect light. Keep moist at all times. A prothallus one generation of the fern will develop first from each spore, forming a light green mat. Mist lightly once a week to maintain high surface moisture; the sperm must be able to swim to the archegonia female parts.

After about three weeks, fertilization should have occurred. Cover with plastic and keep moist. When fern fronds appear and become crowded, transplant to small pots. Gradually reduce the humidity until they can survive in the open.

Light exposure may be increased at this time. Asexual propagation, as mentioned earlier, is the best way to maintain some species, particularly an individual that best represents that species. Clones are groups of plants that are identical to their one parent and that can only be propagated asexually. The Bartlett pear and the Delicious apple are two examples of clones that have been asexually propagated for many years.

The major methods of asexual propagation are cuttings, layering, division, budding and grafting. Cuttings involve rooting a severed piece of the parent plant; layering involves rooting a part of the parent and then severing it; and budding and grafting is joining two plant parts from different varieties. Many types of plants, both woody and herbaceous, are frequently propagated by cuttings. A cutting is a vegetative plant part which is severed from the parent plant in order to regenerate itself, thereby forming a whole new plant.

Take cuttings with a sharp blade to reduce injury to the parent plant. Dip the cutting tool in rubbing alcohol or a mixture of one part bleach : nine parts water to prevent transmitting diseases from infected plant parts to healthy ones. Remove flowers and flower buds from cuttings to allow the cutting to use its energy and stored carbohydrates for root and shoot formation rather than fruit and seed production.

To hasten rooting, increase the number of roots, or to obtain uniform rooting except on soft, fleshy stems , use a rooting hormone, preferably one containing a fungicide. Prevent possible contamination of the entire supply of rooting hormone by putting some in a separate container for dipping cuttings.

Insert cuttings into a rooting medium such as coarse sand, vermiculite, soil, water, or a mixture of peat and perlite. It is important to choose the correct rooting medium to get optimum rooting in the shortest time. In general, the rooting medium should be sterile, low in fertility, drain well enough to provide oxygen, and retain enough moisture to prevent water stress.

Moisten the medium before inserting cuttings, and keep it evenly moist while cuttings are rooting and forming new shoots. Place stem and leaf cuttings in bright, indirect light. Root cuttings can be kept in the dark until new shoots appear. Numerous plant species are propagated by stem cuttings.

Some can be taken at any time of the year, but stem cuttings of many woody plants must be taken in the fall or in the dormant season. Tip cuttings: Detach a 2 to 6-inch piece of stem, including the terminal bud. Make the cut just below a node. Remove lower leaves that would touch or be below the medium. Dip the stem in rooting hormone if desired. Gently tap the end of the cutting to remove excess hormone. Insert the cutting deeply enough into the media to support itself.

At least one node must be below the surface. Leaf sections: This method is frequently used with snake plant and fibrous rooted begonias. Cut begonia leaves into wedges with at least one vein. Lay leaves flat on the medium. A new plant will arise at the vein. Cut snake plant leaves into 2-inch sections.

Consistently make the lower cut slanted and the upper cut straight so you can tell which is the top. Insert the cutting vertically. Roots will form fairly soon, and eventually a new plant will appear at the base of the cutting.

These and other succulent cuttings will rot if kept too moist. Root cuttings are usually taken from 2 to 3 year old plants during their dormant season when they have a large carbohydrate supply. Root cuttings of some species produce new shoots, which then form their own root systems, while root cuttings of other plants develop root systems before producing new shoots. Plants with large roots: Make a straight top cut. Make a slanted cut 2 to 6 inches below the first cut. Store cutting about 3 weeks in moist sawdust, peat moss, or sand at 40 degrees F.

Remove from storage. Insert the cutting vertically with the top approximately level with the surface of the rooting medium. This method is often used outdoors. Plants with small roots: Take 1 to 2 inch sections of roots. Insert the cuttings horizontally about 12 inches below the medium surface.

This method is usually used indoors or in a hotbed. Stems still attached to their parent plants may form roots where they touch a rooting medium. Severed from the parent plant, the rooted stem becomes a new plant. Some plants layer themselves naturally, but sometimes plant propagators assist the process. Layering is enhanced by wounding one side of the stem or by bending it very sharply.

The rooting medium should always provide aeration and a constant supply of moisture. The following propagation methods can all be considered types of layering, as the new plants form before they are detached from their parent plants:.

Air layering: Air layering is used to propagate some indoor plants with thick stems, or to rejuvenate them when they become leggy. Slit the stem just below a node. Pry the slit open with a toothpick. Surround the wound with wet unmilled sphagnum moss. Wrap plastic or foil around the sphagnum moss and tie in place. When roots pervade the moss, cut the plant off below the root ball. Examples: dumbcane, rubber tree.

Simple layering: Bend the stem to the ground. Cover part of it with soil, leaving the last 6 to 12 inches exposed. Bend the tip into a vertical position and stake in place. The sharp bend will often induce rooting, but wounding the lower side of the branch or loosening the bark by twisting the stem may help. Examples: rhododendron, honeysuckle. If the stems are not joined, gently pull the plants apart. If the crowns are united by horizontal stems, cut the stems and roots with a sharp knife to minimize injury.

Divisions of some outdoor plants should be dusted with a fungicide before they are replanted. Examples: dahlias, iris, rhubarb, day lilies. Separation is a term applied to a form of propagation by which plants that produce bulbs or corms multiply. Bulbs: New bulbs form beside the originally planted bulb. Separate these bulb clumps every 3 to 5 years for largest blooms and to increase bulb population.

Dig up the clump after the leaves have withered. Gently pull the bulbs apart and replant them immediately so their roots can begin to develop. Small, new bulbs may not flower for 2 or 3 years, but large ones should bloom the first year. Examples: tulip, narcissus.

Corms: A large new corm forms on top of the old corm, and tiny cormels form around the large corm. After the leaves wither, dig up the corms and allow them to dry in indirect light for 2 or 3 weeks. Remove the cormels, and then gently separate the new corm from the old corm. Dust all new corms with a fungicide and store in a cool place until planting time.

Examples: crocus, gladiolus. Grafting and budding are methods of asexual plant propagation that join plant parts so they will grow as one plant. These techniques are used to propagate cultivars that will not root well as cuttings or whose own root systems are inadequate.

The portion of the cultivar that is to be propagated is called the scion. It consists of a piece of shoot with dormant buds that will produce the stem and branches. The cambium is a layer of cells located between the wood and bark of a stem from which new bark and wood cells originate. See Fruit chapter for discussion of apple rootstock.

Cleft grafting: Cleft grafting is often used to change the cultivar or top growth of a shoot or a young tree usually a seedling. It is especially successful if done in the early spring. Cut the limb or small tree trunk to be reworked, perpendicular to its length. Make a 2-inch vertical cut through the center of the previous cut.

Be careful not to tear the bark. Keep this cut wedged apart. Cut the lower end of each scion piece into a wedge. Prepare two scion pieces 3 to 4 inches long. 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. Saw off the limb or trunk of the rootstock at a right angle to itself.

Leave two buds above the longer cut. Cut through the bark of the stock, a little wider than the scion. Remove the top third of the bark from this cut. Insert the scion with the longer cut against the wood. Nail the graft in place with flat-headed wire nails. Cover all wounds with grafting wax. The scion and rootstock are usually of the same diameter, but the scion may be narrower than the stock.

On the cut surface, slice downward into the stock and up into the scion so the pieces will interlock. Fit the pieces together, then tie and wax the union. Very little success in grafting will be obtained unless proper care is maintained for the following year or two. If a binding material such as strong cord or nursery tape is used on the graft, this must be cut shortly after growth starts to prevent girdling. They expand with growth and usually do not need to be cut, as they deteriorate and break after a short time.

It is also an excellent idea to inspect the grafts after 2 or 3 weeks to see if the wax has cracked, and if necessary, rewax the exposed areas. Limbs of the old variety which are not selected for grafting should be cut back at the time of grafting. The total leaf surface of the old variety should be gradually reduced as the new one increases until at the end of 1 or 2 years, the new variety has completely taken over. Completely removing all the limbs of the old variety 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. Budding, or bud grafting, is the union of one bud and a small piece of bark from the scion with a rootstock. It is especially useful when scion material is limited. It is also faster and forms a stronger union than grafting. Patch budding: Plants with thick bark should be patch budded.

This is done while the plants are actively growing, so their bark slips easily. Remove a rectangular piece of bark from the rootstock. Cover this wound with a bud and matching piece of bark from the scion. Chip budding: This budding method can be used when the bark is not slipping. Make a second cut upward from the first cut, about one inch.

Remove a bud and attending chip of bark and wood from the scion shaped so that it fits the rootstock wound. Fit the bud chip to the stock and wrap the union.

When the bark is slipping, make a vertical cut same axis as the root stock through the bark of the rootstock, avoiding any buds on the stock. Make a horizontal cut at the top of the vertical cut in a T shape and loosen the bark by twisting the knife at the intersection. Remove a shield-shaped piece of the scion, including a bud, bark, and a thin section of wood. Push the shield under the loosened stock bark. Wrap the union, leaving the bud exposed. Place the bud in the stock in August.

Propagation | of plants | animalsexotique.com

Edited and revised by David C. Plant propagation is the process of creating new plants. There are two types of propagation: sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual. Sexual propagation involves the floral parts of a plant.

Asexual propagation involves taking a part of one parent plant and causing it to regenerate itself into a new plant. The resulting new plant is genetically identical its parent. Asexual propagation involves the vegetative parts of a plant: stems, roots, or leaves. It may be easier and faster in some species; it may be the only way to perpetuate some cultivars; and it bypasses the juvenile characteristics of certain species. Sexual propagation involves the union of the pollen male with the egg female to produce a seed.

The seed is made up of three parts: the outer seed coat, which protects the seed; the endosperm, which is a food reserve; and the embryo, which is the young plant itself.

When a seed is mature and put in a favorable environment, it will germinate begin active growth. In the following section, seed germination and transplanting of seeds will be discussed. Adapted from J. Harrington and P. Seed To obtain quality plants, start with good quality seed from a reliable dealer. Select varieties to provide the size, color, and habit of growth desired.

Choose varieties adapted to your area which will reach maturity before an early frost. Quality seed will not contain seed of any other crop, weeds, seeds, or other debris. If seeds are obtained well in advance of the actual sowing date or are stored surplus seeds, keep them in a cool, dry place.

Laminated foil packets help ensure dry storage. The door shelves in a refrigerator work well. Some gardeners save seed from their own gardens; however, such seed is the result of random pollination by insects or other natural agents, and may not produce plants typical of the parents. This is especially true of the many hybrid varieties. See UMaine Extension Bulletin for information on how to save your own seed. Germination will begin when certain internal requirements have been met.

A seed must have a mature embryo, contain a large enough endosperm to sustain the embryo during germination, and contain sufficient hormones to initiate the process. There are four environmental factors which affect germination: water, oxygen, light, and heat. The first step in the germination process is the imbibition or absorption of water. Even though seeds have great absorbing power due to the nature of the seed coat, the amount of available water in the substrate affects the uptake of water.

An adequate, continuous supply of water is important to ensure germination. Once the germination process has begun, a dry period can cause the death of the embryo. Light is known to stimulate or to inhibit germination of some types of seed. The light reaction involved here is a complex process.

Some crops which have a requirement for light to assist seed germination are ageratum, begonia, browallia, impatiens, lettuce, and petunia. Conversely, peas, beans, calendula, centaurea, annual phlox, verbena, and vinca will germinate best in the dark.

Other plants are not specific at all. Seed catalogs and seed packets often list germination or cultural tips for individual varieties. When sowing light-requiring seed, do as nature does, and leave them on the soil surface.

If they are covered at all, cover them lightly with fine peat moss or fine vermiculite. These two materials, if not applied too heavily, will permit some light to reach the seed and will not limit germination. When starting seed in the home, supplemental light can be provided by fluorescent fixtures suspended 6 to 12 inches above the seeds for 16 hours a day.

In all viable seed, respiration takes place. The respiration in dormant seed is low, but some oxygen is required. The respiration rate increases during germination, therefore, the substrate in which the seeds are placed should be loose and well-aerated. If the oxygen supply during germination is limited or reduced, germination can be severely retarded or inhibited. A favorable temperature is another important requirement of germination. Some seeds will germinate over a wide range of temperatures, whereas others require a narrow range.

Many seeds have minimum, maximum, and optimum temperatures at which they germinate. For example, tomato seed has a minimum germination temperature of 50 degrees F. Where germination temperatures are listed, they are usually the optimum temperatures unless otherwise specified. Generally, 65 to 75 degrees F. This often means the germination flats may have to be placed in special chambers or on radiators, heating cables, or heating mats to maintain optimum temperature.

One of the functions of dormancy is to prevent a seed from germinating before it is surrounded by a favorable environment. In some trees and shrubs, seed dormancy is difficult to break, even when the environment is ideal.

Various treatments are performed on the seed to break dormancy and begin germination. Seed scarification involves breaking, scratching, or softening the seed coat so that water can enter and begin the germination process. There are several methods of scarifying seeds. In acid scarification, seeds are put in a glass container and covered with concentrated sulfuric acid.

The seeds are gently stirred and allowed to soak from 10 minutes to several hours, depending on the hardness of the seed coat. When the seed coat has become thin, the seeds can be removed, washed, and planted.

Another scarification method is mechanical. Seeds are filed with a metal file, rubbed with sandpaper, or cracked with a hammer to weaken the seed coat. Hot water scarification involves putting the seed into hot water to degrees F.

The seeds are allowed to soak in the water, as it cools, for 12 to 24 hours and then planted. A fourth method is one of warm, moist scarification. In this case, seeds are stored in nonsterile, warm, damp containers where the seed coat will be broken down by decay over several months. Seeds of some fall-ripening trees and shrubs of the temperate zone will not germinate unless chilled underground as they over winter.

The following procedure is usually successful. Put sand or vermiculite in a clay pot to about 1 inch from the top. Wet the medium thoroughly and allow excess water to drain through the hole in the pot. Place the pot containing the moist medium and seeds in a plastic bag and seal.

Place the bag in a refrigerator. Periodically check to see that the medium is moist, but not wet. Additional water will probably not be necessary. After 10 to 12 weeks, remove the bag from the refrigerator. Take the pot out and set it in a warm place in the house. Water often enough to keep the medium moist. Soon the seedlings should emerge. When the young plants are about 3 inches tall, transplant them into pots to grow until time for setting outside.

Another procedure that is usually successful uses sphagnum moss or peat moss. Wet the moss thoroughly, then squeeze out the excess water with your hands.

Mix seed with the sphagnum or peat and place in a plastic bag. Seal the bag and put it in a refrigerator. Check periodically. If there is condensation on the inside of the bag, the process will probably be successful. Plant the seeds in pots to germinate and grow. Handle seeds carefully. Often the small roots and shoots are emerging at the end of the stratification period.

Care must be taken not to break these off. Temperatures in the range of 35 to 45 degrees F 2 to 70C are effective. Seeds of peaches should be removed from the hard pit. Care must be taken when cracking the pits. Any injury to the seed itself can be an entry path for disease organisms. A wide range of materials can be used to start seeds, from plain vermiculite or mixtures of soilless substrates to the various amended soil mixes. With experience, you will learn to determine what works best for the seeds that you are starting.

When choosing a substrate its important to keep in mind what the good qualities of a germinating substrate are. It should be rather fine and uniform, yet well-aerated and loose. It should be free of insects, disease organisms, and weed seeds.

Sexual propagation

Sexual propagation

Sexual propagation