Andromeda Botanic Gardens 

 

Plant Propagation

 

Plant propagation is the process of producing new plants. There are a number of ways in which new plants can be created. New plants can be produced by sexual or asexual (vegetative) means.  

Scroll through the entire page to view discussions and links on various sexual and asexual plant propagation methods, or follow the bookmarks below to get directly to each topic (use the "Back" button to return to the top of the page).

Sexual Methods of Plant Propagation Asexual (Vegetative) Methods of Plant Propagation

 

 

Student Practicals in Progress

 

 

Sexual Methods of Plant Propagation:

Sexual methods of propagation involve producing new plants from seeds or spores.

Advantages of Using Sexual Methods of Propagation

  1. Sexual propagation methods are often the cheapest way of producing a large number of plants.

 

  1. When using sexual methods of propagation, variation occurs and new cultivars, (cultivated types of plants) may be created. The new plants may have different and exciting colours, shapes and sizes.

 

 

Disadvantages of Using Sexual Methods of Propagation :

 

  1. Plants grown by sexual methods may take longer to reach maturity.

 

  1. Variation is not always good, desirable characteristics of the parent plants may be lost.

   

 

Seeds:

The most common way of propagating plants is by seed. Many plants produce large numbers of seeds, (an orchid seed pod can contain 3 million!), each of which can be grown to produce a new plant.

Students of the Grantley Adams Memorial School planting seeds at the Andromeda Botanic gardens.

Seeds are generally made up of three parts, the embryo (young plant), food storage tissue, and the seed covering.

Cotyledons, (seed leaves), are attached to the embryo. The number of cotyledons present may be used as a means of classifying seeds.

Monocotyledons (monocots) are seeds, which have one cotyledon, e.g. palms, grasses and corn.

Dicotyledons (dicots) are seeds, which have two cotyledons, e.g. peas and beans.

Gymnosperms have seeds, which may contain up to fifteen cotyledons, e.g. pine trees.

 

Germinating Seeds:

The seed covering consist of the seed coat (testa), and parts of the fruit or seedpod. These structures protect the embryo and food reserve inside the seed. The seed covering also functions to prevent the seed from germinating until conditions in its surroundings are favorable for germination and seedling development to occur.

Favorable conditions for germination vary from seed to seed. Seeds germination may be affected by temperature, light, water and air conditions.

Germinated pussy vine (Clitoria sp.) seedlings.

Some seeds may remain dormant (fail to germinate), unless exposed to some types of stress, before germination will occur. Scarification and stratification are techniques commonly used to encourage germination in some seeds.

 

Scarification involves breaking or scarring the hard seed coat. Scarification may be achieved mechanically by using sandpaper, a knife, pliers or a hammer. Scarification may also be achieved chemically by dipping seeds in Sulphuric acid. These types of stresses may mimic nature where seed coats may be scarred by exposure to the elements over time, or exposed to acid in the digestive tracts of birds and animals.

 

Stratification involves exposing seeds to a moist chilling treatment to overcome dormancy. Stratification may be necessary to germinate seeds from cold countries, where exposure to a period of cold and then moist conditions may signal that spring is coming, and it is safe for seeds to germinate.

 

Sowing Seeds:

 

The depth to which seeds are sown (planted) differs from seed to seed. Those seeds requiring light for germination need to be planted nearer the surface. Generally seeds should not be planted deeper than two or three times their diameter. Larger seeds like coconuts can be partly covered in the soil and kept moist.

To learn more about propagating plants from seeds, follow the links below, or visit us at Andromeda for practical demonstrations.

http://edis.ifas.ufl.edu/MG276

http://www.hcs.ohio-state.edu/mg/manual/prop.htm

   

Spores:  

Most ferns grow form spores. Spores are formed in sporangia (dark spots on the underside of of fern fronds/leaves). Spores are very small and seed-like. Spores can be collected from mature brown sporangia by shaking the frond over a piece of paper. If the sporangia are green, they are immature, and the frond can be placed in an envelope for the sporangia to mature before collecting the spores.

Spores need a moist environment for germination. A simple method for germinating spores will be highlighted here.   

  • Soak a clay flowerpot, peat-pot or peat pellet in water and stand it upside down in a saucer or dish with water at the bottom

  • Sprinkle fern spores on the sides and top of the pot or peat pellet

  • Cover with clear plastic (to prevent mold or fungal spores from settling on the pot or pellet)

  • Place in a bright area away from direct sunlight (keeping water in the dish or saucer at all times)

In about six weeks the pot should turn green with the germinating spores. Small leaf-like prothalli should appear first, followed in a few weeks by tiny fern fronds. At this point the young ferns can be carefully removed and planted elsewhere. The young ferns will need a warm, moist and shady environment to develop further.

Propagating from spores will have similar advantages and disadvantages to propagating from seeds (as mentioned above).   

Follow the links below to learn more about ferns, their life cycles and propagation.

http://scitec.uwichill.edu.bb/bcs/bl14apl/bl14apl.htm

http://www.hcs.ohio-state.edu/mg/manual/prop.htm

 

Asexual (Vegetative) Methods of Plant Propagation:

 

Asexual or vegetative propagation refers to producing new plants without any fertilization occurring. Vegetative methods of plant propagation include the use of cuttings, budding, grafting, air layering, tissue culture and propagation by division.

 

Advantages of Vegetative Propagation:

 

·            Exact copies of parent plants can be produced in most cases (conserving desired characteristics)

·           Often simple and relatively quick

·           Large plants can sometimes be produced in a short period of time

·           Good quality and uniformity among plants produced

 

Disadvantages of Vegetative Propagation:  

 

·            All offspring share common susceptibility to disease

·            Not suitable if variation is desired

 

Plant Propagation by Cuttings:

 

  • A cutting is a cut piece of plant material, which can be made to develop new stems and roots to form a new plant.

   

  • Stems, leaves or roots may be used as a source of cutting material.

 

  • Cuttings should only be selected from healthy plants, which have desirable characteristics and are free of pest and diseases.

 

  • Cuttings must be provided with the right temperature, nutrition and moisture levels for rooting and shoot development to occur.

 

  • Auxins (plant growth regulators) are often used to encourage rooting in cuttings. Auxins encourage cell division and elongation, which are important for callus formation.                                                  
  • Auxins also promote root formation.

 

  • Cuttings are commonly rooted in sand, perlite, vermiculite, peat moss or various mixtures of the preceding. Some cuttings may also be rooted in plain water.

 

 

 

Types of Cuttings:

  1. Stem Cuttings:

 

Stem cuttings may be made from the stem tip or from sections of stems of many plants.  

Students from the St. Lucy Secondary School preparing cuttings at the Andromeda Botanic Gardens.

·        Stem tip cuttings may be taken from the top 7 to 10 centimetres of the stem. The cut should be made just below a node. Any leaves at the base that would be covered with the rooting medium should be removed. Cuttings should then be placed upright in a rooting tray or pot in a warm bright area. It may be necessary to cover some cuttings with plastic for a few days to maintain conditions of high humidity (to prevent the cuttings from drying out and dying). Cuttings should be watered regularly until roots develop. Plants suitable for propagation by tip cuttings include yellow sage, blue plumbago and coleus (Joseph’s coats).

 

·        Stem section cuttings are useful for propagating many ornamental plants. Often sections of stem between 10 to 20 centimetres are used. If leaves are present, all but a few of them should be removed to reduce water loss by the stem from the leaf surfaces. Clean slanted cuts should be made at the base, and each section should contain at least two nodes (from which new roots and shoots may arise). The base the cuttings should be inserted about 2.5 centimetres into the rooting medium. The cuttings should be placed in a warm bright area and kept moist until rooting occurs. Crotons and bougainvilleas are often propagated in this manner.

 

·        Cane cuttings are a special type of stem cutting used in plants, which produce cane-like or leafless stems. Leafless stem sections (7 to 10centimetres long), and having at least two buds, are cut from older stems. These cutting are placed horizontally (on their sides), slightly below the surface of the rooting medium. Roots and new shoots subsequently develop. Plants suitable for propagation by cane cuttings include dumb cane (dieffenbachia sp.) and dracaenas.  

 

For more information on stem cuttings, follow the link below.

http://www.ces.ncsu.edu/depts/hort/hil/hil-8702.html

 

  1. Leaf Cuttings:

 

Some plants can be propagated from a whole leaves or part of a leaf. Leaf cuttings are not suitable for propagating most plants because leaf cuttings generally lack auxiliary buds from which adequate roots and shoots may develop. The leaves of most plants only produce a few roots before dying, or just decay

Leaf cuttings are suitable for propagating plants, which are capable of producing adventitious buds.

There are a number of types of leaf cuttings including whole leaf, leaf-petiole, leaf section, split-vein and leaf bud cuttings.

·        Whole leaf cuttings may or may not include the petiole (leaf stalk). The leaf base may be partially submerged in the rooting media. Roots and leaves may then arise from the leaf base.

Peperomias and some begonias may be propagated in this way.

 

·        Leaf-petiole propagation involves planting a leaf with up to 4cm of petiole. The petiole is inserted into the medium, and new roots and leaves arise from its base. Some African violets and peperomias may be grown in this way.

 

·        Leaf section propagation involves planting cut sections of leaves. This method is used for plants with thick fleshy leaves. Cut sections up to 10 centimetres long are inserted vertically (upright) in the rooting medium. This method is used for propagating Sansevieria (Snake plant or Mother in laws tongue).

 

A rooted leaf section cutting of the snake plant (Sansevieria sp.).

   

  1. Root Cuttings:

 

Some plants are suitable for propagation from root cuttings.

Cuttings from plants with large roots should be 5 to 15 centimetres long. These cuttings should be planted 5 to 7 centimetres apart with the proximal end (end from nearest the crown of the plant) buried 5 to 7 centimetres below the rooting medium.

Cuttings from plants with small roots should be 3 to 5 centimetres long. These cuttings can be placed horizontally (on their sides) about 2 centimetres below the rooting medium.

Breadfruit trees are commonly propagated from root cuttings.  

For more on propagation from leaves and roots, follow the link below.

http://www.ces.ncsu.edu/depts/hort/hil/hil-8700.html

 

 

 

Budding and Grafting:

 

Budding and grafting are two asexual (vegetative) propagation techniques involving joining parts from two or more plants, so that they grow as one.

These techniques are especially useful for propagating plants that are difficult to root from cuttings, or that tend to develop poor root systems.

One or more new cultivars may be added to an existing fruit tree by budding or grafting.

 

The plant part that is to be propagated is referred to as the scion. The scion consists of a piece of shoot with a dormant bud, or buds, which may develop into new stems and branches.

The plant that is to provide the scion with a root system is referred to as the rootstock or stock plant.

 

In order for budding and grafting techniques to be successful the following conditions must be met:

 

·         The scion and rootstock must be compatible. Budding and grafting generally only work with closely related plants. All citrus cultivars (oranges, lemons, grapefruit e.t.c.) may be grafted onto each other, and all mangoe cultivars may be grafted onto each other, but a citrus graft will not “take” (develop successfully) on a mango rootstock.

 

·         The cambial layers of both scion and rootstock must come into contact with each other. The cambium is the layer of cells between the wood and the bark of a stem from which new bark and wood cells arise.

 

·         The scion and rootstock must be at the proper physiological stage. The scion is most often selected from physiologically mature parts of the parent plant, so that the developing stems would be physiologically mature as well.

 

 

·         The bud or graft union must be kept moist until the wound has healed.

 

 

Grafting:

 

Grafting involves using a scion with a number of dormant buds that will produce new stems and branches.

 

Grafting is useful for:

 

·         Changing the cultivars or variety of an existing orchard (for example going from lemon production to lime production without having to replant trees). This technique is commonly referred to as topworking.

 

·         Repairing trees from which limbs have broken off (limbs replaced by grafting)

 

 

·         Conserving desired characteristics (the scion will grow exactly like the plant from which it originated)

 

·         Adding a branch of a new cultivar for observation and testing (before going into large scale production of the new cultivar)

 

There are a number of different grafting techniques including cleft grafting, bark grafting and whip or tongue grafting.

 

Follow the links below for more information and diagrams illustrating various grafting techniques.

 

http://ag.arizona.edu/pubs/garden/mg/propagation/grafting.html

http://aggie-horticulture.tamu.edu/propagation/cleftgrafting/cleftgrafting.html

http://aggie-horticulture.tamu.edu/propagation/approachgraft/approach.html

 

 

 

Budding:

 

Budding is a special form of grafting in which only a single bud is used as the scion.

 

  • Budding is especially useful when scion material is limited

 

  • Budding forms stronger unions than grafting

 

  • Budding is often faster than other grafting techniques

 

 

There are a number of different budding techniques including patch budding, chip budding and T budding.

Budding is commonly used in Barbados for propagation of citrus plants (oranges, lemons, limes, grapefruit e.t.c.).

 

Follow the links below for more information and diagrams illustrating various budding techniques.

http://aggie-horticulture.tamu.edu/propagation/budding/budding.html

http://aggie-horticulture.tamu.edu/citrus/budding/budding.htm

http://ag.arizona.edu/pubs/garden/mg/propagation/grafting.html

 

 

 

Layering:

 

Layering is a vegetative propagation method where plants are encouraged to develop roots on stems, which are still attached to a parent plant. The “layer” (rooted stem) can then be removed from the parent plant and planted elsewhere.

 

Layering is useful for:

 

  • Propagating hard to root plants

 

  • Producing relatively large plants in a short time (depending on the plant being layered)

 

 

 

Layering is limited by:

 

  • Availability of stems on which to develop layers

 

 

Layering usually involves wounding the stem or branch at the point where roots are to be encouraged to develop.

 

Types of Layering:

 

There are a number of layering techniques including simple layering, tip layering, compound (serpentine) layering, mound (stool) layering and air layering.

 

  • Simple Layering:

 

Simple layering involves bending a low-lying flexible branch to the ground.

The branch is then wounded (part of the bark removed) on its lower side, about 15 to 30 centimetres below the tip.

The wounded area is the covered with soil and staked in position.

The tip is bent into a vertical (upright) position.

Roots are expected to develop in the soil-covered area.

After satisfactory rooting has occurred, the layers can be cut out and transplanted.

Climbing roses can be propagated from simple layers.

 

  • Tip Layering:

 

Tip layering is similar to simple layering, but the shoot tip is covered in the soil instead of part of the stem.

The tip grows downwards then bends up sharply.

Roots form at the bend.

 

  • Compound (Serpentine) Layering:

 

Compound layering is similar to simple layering, but several layers can be produced on a single stem.

A flexible stem is bent to the ground as in simple layering, but sections of the stem are alternately covered with soil (with their lower sides wounded) or exposed.

Each section should have at least one bud exposed (for new shoot development), and one bud covered with soil (for new root development).

Vine-line plants like philodendrons and pothos are suitable for propagation by this method.

 

  • Mound (Stool) Layering:

 

Mound layering is used with heavy-stemmed, closely branched rootstocks of some fruit trees.

The stock is cut back to about 2.5 centimetres above the soil surface.

Dormant buds would then be allowed to shoot.

Soil is mounded over the new shoots as they grow.

Roots will develop at the base of the young shoots.

The shoots (the layers in this case) can then be removed once adequate root development has occurred.

 

  • Air Layering:

 

Air layering is useful for improving the appearance of plants which have become “leggy” through the loss of their lower foliage (by removing some of he bare sections of stem).

Air layering is also useful for propagating some woody and hard to root species.

A section, or entire ring of bark from an area of stem (from 3 to 6 centimetres) is removed.

Some rooting hormone may be applied to the upper base of the cut to encourage root formation.

The exposed area is covered with damp peat moss, or some other damp rooting medium.

The rooting medium is then wrapped in plastic or foil so that it would remain moist.

The ends of the wrapping are securely fastened so that it remains in place.

Once roots have grown through the rooting media, the layer can be removed and transplanted.

            This technique is often used to propagate ficus plants and dracaenas.

A student of the Lodge School air layering a ficus plant at the Andromeda Botanic Gardens.
 
  • Natural Layering:

 

Some plants produce layers naturally.

These layers may be referred to as runners or offsets.

Spider plant is an example of a plant propagated in this way.

These plants will be considered in greater detail under propagation by division.

 

 

Follow the links below for more information on layering, and diagrams illustrating the various techniques.

http://www.ces.ncsu.edu/depts/hort/hil/hil-8701.html

http://aggie-horticulture.tamu.edu/extension/ornamentals/airlayer/airlayer.html

 

 

 

Plant Propagation by Division:

Plant propagation by division includes a number of different techniques, in each of which the parent plant is split into two or more pieces, each capable of developing into a new plant. These techniques are all asexual (vegetative), so all new plants produced will have identical characteristics to the parent plant.

Propagation by division is common in two types of plants, those with a clumping growth habit, and bulbous plants (plants with specialized storage organs, above or below the ground, including bulbs, corms, rhizomes, stolons, tubers and pseudobulbs).

Propagating Plants with a Clumping Growth Habit:

Plants suitable for propagating in this manner often have multiple stems or grow in clumps. Propagation of these plants if often a simple process involving digging up the clump and dividing it into pieces with adequate roots. The pieces can then be replanted to the same depth below the soil from which they were dug. Common ornamental plants propagated from division include orchids, bamboo, liriope, zamias and bromeliads.

Propagating Bulbous Plants:

Storage organs are a common feature of bulbous plants. These storage organs aid plants in surviving long periods of stress in their environment (such as heat or drought). The nutrients stored in these organs also support regrowth of roots and shoots after the period of stress has passed. Some of these storage tissues can be used for propagating new plants. 

  • Bulbs are stem tubers. They are composed of a short fleshy vertical stem, covered by thick fleshy modified leaves (called scales or bud scales). Buds have a basal plate from which new growth arises. The fleshy scale leaves protect the bulb, and these leaves in turn may be covered by a thin outer membrane called a tunic. Bulbs with a tunic (like onions) are better protected from drying out and other damage than those without (like lily bulbs). Plants commonly grown from bulbs include crinums and spider lilies. 

 

  • Corms are modified stems. Corms are covered by dry scale-like leaves (a tunic), but differ from true bulbs in having distinct nodes and internodes. Corms are propagated by separating offsets (called cormels) from the primary corm. Corms produce two types of roots, fibrous roots for water and nutrient uptake, and enlarged roots for support and pulling the corm deeper into the soil for more uniform temperatures. The carbohydrates stored in corms tend to become depleted as new shoots grow and develop. New corms then tend to be created by the plant just below the original corm. New cormels may also develop at the base of the new corm. Gladiolus is grown from corms.

 

  • Rhizomes and Stolons are both horizontal modified stems. Rhizomes grow horizontally below the soil, while stolons grow horizontally above the soil surface. Rhizomes and tubers are commonly produced in monocots (like grasses), but some dicots and ferns produce them as well. rhizomes and stolons may yield multiple plants, but each division must include a vegetative bud for development to be successful.

 

  • Tubers refer to modified stems (stem tubers) and roots (root tubers). Stem tubers grow underground and have nodes and axillary buds (eyes). Buds near the shoot end (terminal buds) may be dominant over buds further away from the shoot. Common examples of stem tubers are the Irish potato and caladiums. Root tubers lack nodes and axillary buds. The buds in root tubers are usually only found at the shoot end of the roots on which they develop. Sweet potatoes can be propagated from root tubers.

 

  • Pseudobulbs or "false bulbs" are very variable modified stems used by some plants for food storage. Pseudobulbs develop in some orchid species. In Dendrobium orchids they arise as offshoots (referred to as keikis) at the upper nodes of the plant. Roots form at the base of the keikis, which may then be removed and planted. In Cattleya orchids, propagation involves using rhizomes or stolons containing four or five pseudobulbs, after the plants have flowered, or as roots start to develop on the pseudobulbs.

Follow the links below for more information and diagrams on plant propagation by division. 

http://edis.ifas.ufl.edu/BODY_MG361

http://farrer.riv.csu.edu.au/ASGAP/division.html

 

 

Tissue Culture:

Tissue culture involves regenerating whole plants from a single cell or very small pieces of plant tissue (like shoot tips, leaf pieces, root pieces, lateral buds and stem sections). Regeneration of new plants is encouraged by rearing cells on specific culture media under sterile conditions. The culture medium generally consist of nutrients (organic and inorganic salts), an energy source (often sucrose or other sugars) and growth regulators (to encourage cell division and differentiation).   

A wide variety of techniques are used in tissue culture, depending on the plant being propagated.

Successful propagation from tissue culture generally requires very sterile conditions, specific culture media and sophisticated laboratory facilities. Tissue culture is therefore not widely practiced. Tissue culture is often limited to purpose built facilities.

Tissue culture can however be achieved in the school lab or home. The first two links below highlight some plant types that have been propagated successfully, and the tissue culture methods used in the classroom situation.

Follow the links below for more information and diagrams on plant tissue culture.

http://ag.arizona.edu/pubs/garden/mg/propagation/grafting.html

http://www.accessexcellence.org/LC/ST/st2bgplant.html

http://www.home.turbonet.com/kitchenculture/tcinfo.htm

 

 

 

 

Copyright © 2003 Stephen Proverbs ( c/o University of the West Indies, Cave Hill Campus). All rights reserved.
Revised: June 14, 2004 .