PROPAGATION I

Learn to Propagate all Types of Plants

• Understand the techniques and equipment
• Learn to select the most appropriate propagation method for the cultivar (variety) of plant you wish to grow.
• Multiply the plants you already have (in your garden or nursery)
• Develop your passion as a hobby, business or employment opportunity.

Lesson Structure

There are 10 lessons in this course:

1. Introduction to Propagation
   • Asexual and sexual propagation
   • Aseptic Micropropagation, Runners, Suckers, Layering, Separation, Division, Grafting, Budding, Cuttings, Seed
   • Genotype versus Phenotype
   • Plant life cycles -phases of the sexual cycle; phases of the asexual cycle
   • Annual, Perennial, Biennial Life Cycles
   • Propagation Terminology
   • Nursery production systems
   • Operational Flow Chart for Seed Propagation
2. Seed Propagation
   • Seed Sources
   • Maintaining Genetic Identity of Seed -Isolation, Rogueing, Testing, Hand Pollination
   • Hybrid Seed Production
   • Storing Seed
   • Types of Seed Storage
   • Seed Biology -Endospermic, Non Endospermic
   • Dormancy Factors Affecting Germination
   • Germination Treatments -boiling water, stratification
   • Terminology
   • Seed Raising Technique
3. Potting Media
   • Characteristics of Potting and Propagating Media
   • Media derived from rock or stone
   • Media derived from synthetics
   • Organic Media
   • Soil Media
   • The UC System
   • Chemical Characteristics -eg. pH, Cation Exchange Capacity, Salinity, Conductivity
   • Laboratory Testing of Media
   • Physical Characteristics
   • Potting Mixes
   • Propagating Media
   • Nutrition at the Propagation Stage
   • Nutrition Management and Fertiliser Application
4. Vegetative Propagation I
   • Reasons to propagate by cuttings
   • Types -softwood, hardwood, semi hardwood, herbaceous
   • Stem Cuttings, Tip, heel, nodal, basal
   • Leaf and Leaf-bud cuttings
   • Cane cuttings
   • Root Cuttings
   • Bulb Cuttings
   • Hormone Treatments for Cutting Propagation
   • Other Cutting Treatments; basal wounding, anti-transpirants, fungicides, disinfectants, mycorrhiza, etc
   • Artificial Light for Propagation
   • Cutting Propagation Efficiency
   • Rockwool Propagation
5. Vegetative Propagation II
   • Care of stock plants
   • Layering
   • Division
   • Terminology
   • Managing Watering
6. Vegetative Propagation III
   • Terminology
   • Budding and grafting
   • Reasons for Grafting
   • How a Graft forms
   • Grafting Techniques; Types of Grafts
   • What Plant to Graft on What
   • Grafting Materials
   • Root Grafting, Bench Grafting, Soft Tissue Grafting
   • Establishing Rootstocks
   • Tissue culture: Applications, Problems, Nutrient Media, Cleanliness, Growing Conditions
   • Tissue Culture Procedures and Techniques
   • Laboratory Requirements
   • Terminology
   • Biotech applications in Horticulture
7. Propagation Structures and Materials
   • Growing in a Greenhouse
   • Growing Structures: Types of Greenhouses, Cold Frames, Shadehouses
   • Propagating equipment -Heaters, Bottom Heat, Misting, Light Control, Benches etc
   • Managing a Greenhouse
8. Risk Management
   • Nursery hygiene
   • Risk assessment and management
   • Safety -tools, equipment handling, electricity, etc
   • Pest and Disease Management
   • Environmental Problems and Management
9. Nursery Management I
   • Plant modification techniques
   • Management policies
   • Keeping Propagation Records
   • Nursery Production Systems
10. Nursery Management II
    • Nursery standards, cost efficiencies, site planning and development

Aims

• Develop the ability to source information on plant propagation, through an awareness of industry terminology and information sources.
• Plan the propagation of different plant species from seeds, using different seed propagation methods.
• Plan the propagation of different types of plants from cuttings, using different cutting propagation methods.
• Plan the propagation of various types of plants using a range of propagation techniques, excluding cuttings and seed.
• Determine the necessary facilities, including materials and equipment, required for propagation of different types of plants.
• Determine a procedure to minimise plant losses during propagation.
• Determine the management practices of significance to the commercial viability of a propagation nursery.
• Design a propagation plan for the production of a plant.

Introduction to Propagation

There are many different ways of producing plants though most plants are produced commercially by either seed or cutting propagation. "Tissue culture" or "Micropropagation" techniques carried out in a laboratory are sometimes used where very large numbers of one plant variety are required quickly. Other plants (eg. roses, deciduous fruit and ornamental trees) are traditionally produced by budding and grafting onto seed or cutting grown rootstocks. Division and separation are commonly used for the propagation of bulbs and herbaceous perennials.

Other propagation techniques (eg. layering or marcotting) may be important in the propagation of some specific types of plants; however they are relatively insignificant when taking a broad view of the nursery industry.

PROPAGATION EFFICIENCY

A skilled propagator can propagate large numbers of plants very quickly and with minimum losses (due to disease, rough handling, poor techniques, etc). If a propagator can get cuttings to strike faster, seed to germinate quicker or more fully, or grafts to "take" (ie. grow together) sooner, then the plants are produced in less time, take up less space in the nursery, require less nurturing, and hence profitability can be increased significantly. The quality and quantity of work achieved by a propagator can vary greatly from nursery to nursery. It is not uncommon for one good propagator to produce the same as three propagators at another nursery.

Improving Propagation Efficiency

There are several factors which affect the efficiency achieved in the production of seedlings or rooted cuttings. These include:


Quality of work

• Has propagating equipment and containers/trays been cleaned/sterilised?
• Has the propagating mix been mixed thoroughly and sterilised?
• Have the seeds or cuttings been correctly labelled?

Cuttings

• How well is the cutting prepared and planted?
• Has the propagator damaged the cutting material excessively? (This would increase the likelihood of pest or disease damage).
• Has the correct amount of leaf been removed?
• Has the cutting been placed in the propagating media properly?
• Has the cutting been treated in a way which will minimize drying out throughout the cutting operation?

Seed

• Has viable (fresh) seed been used?
• Has the seed been adequately separated from fruits or pods?
• Has the seed been sown evenly and at a suitable density? Seeds sown too heavily will be overcrowded and consequently of poorer quality. Seeds sown too thinly waste valuable space and materials.
• Has the seed been sown at a suitable depth? More seeds are lost from sowing too deeply than by sowing at too shallow a depth.
• Seeds sown deeply will also take longer to emerge after germination. A seed only has a certain amount of resources stored within in to allow it to germinate and make it above the soil. If a seed is sown too deeply, it will run out of resources before it emerges and is able to photosynthesise.

Selection of the most appropriate technique

Consider

• What time of the year is the operation carried out?
• What type of propagating media is used? (eg. sand/peat, sand, vermiculite, growool, open ground, perlite bed, gravel bed, nutrient agar ...etc?).

Cuttings -  What type of cutting is used? (eg. semi-hardwood, hardwood, softwood, tip cuttings, older wood, leaf bud, leaf, root, 4 cm long, 6 cm long...etc?).  What additional treatments have been carried out on the cuttings? (eg. hormones, disinfecting drenches).

Seed - Has a suitable pre-germination treatment been used (eg. scarification, stratification, hot water)?

After care

Where are the seed trays or cuttings placed after planting? Are they outside exposed to the elements, in a glasshouse, in a cold frame, in a hot bed, etc?
How frequently are they watered? Are they watered by hand, by manual sprinklers, or by automatic sprinklers?

Growth stimulation -  Have any techniques been used to stimulate germination or root growth (eg. bottom heat, wounding, intermittent misting, fogging)?

Cost of materials used

Are the seed or cuttings placed in a pot, in a bed or in the ground?
How many seed or cuttings can be fitted into a particular space? More cuttings or seeds per unit space is more cost efficient as long as you don't have overcrowding.
How much doe the materials cost? This includes cost of pots, propagating mix, labels, hormones, greenhouses, hotbeds, etc.

Labour cost

Do you have ready access to propagation material? Consider the time involved obtaining seed or cuttings.
How many seeds can you sow, or cuttings can you prepare and plant per hour?
What time is involved in after care....watering, weeding, spraying, fertilising, etc.
Are the propagation greenhouses close to the propagating area...does it take time to transfer cuttings or seed trays from one area to another?
Variety of plant (some plants may require more attention than others to look after).

Success Rate

What proportion of seeds germinate, or cuttings planted actually form roots?
How long does it take for the seeds to germinate or for cuttings to form roots?
This must be related back to the cost of the space... do the cuttings or seed take up a lot of space in a hotbed, consider that the hotbed costs money to buy and costs money to run. The seed which germinates more quickly or cuttings which strike faster are generally less expensive to produce.

Variety being propagated (Some varieties of plants are more likely to be successful than others).

All of these factors (and others) will have a bearing on the cost of producing a plant from seed or by cutting. Some of these factors will be more significant than others. Some may account for 10, 20 or 30% of the cost; others might only account for a very small proportion of the cost.





SEXUAL PROPAGATION

Sexual propagation involves growing a plant from a seed or spore which has been produced by fertilization of the female part of one plant by the male part. Plants grown this way can have some characteristics of one parent... and some characteristics from the other parent. A sexually propagated plant is not always exactly the same as the plant from which the seed or spores was taken.

Most flowering annuals, vegetables, biennials and perennials are grown this way. Ferns and some trees and shrubs are also grown sexually.

Some types of seeds are much more difficult to germinate than others. In their natural state most species have adopted mechanisms which allow germination to occur with relative ease. For many "difficult to germinate seeds", it is possible to carry out some type of pre-germination treatment which will increase the chances of success.



Dormancy Factors Affecting Germination

1. Physical Dormancy

Seed coats, and sometimes hardened sections of other parts of the seed becomes impermeable to water. In nature these hard layers are softened by environmental effects such as freezing and thawing, mechanical abrasion, attack by micro‑organisms, etc. This condition is characteristic of many plant families, including Fabaceae, Malvaceae, Geraniaceae, and Solanaceae.

2. Mechanical Dormancy

The seed covering is too hard to allow embryo to expand when germinating (eg. in a peach stone).

3. Chemical Dormancy

Chemicals in the seed inhibit germination. This is common with fleshy fruits and berries. Seeds of this type usually need to be removed from the fruit and washed before sowing.

4. Morphological Dormancy

The seed is not fully developed at the time the fruit ripens. It needs time before it can be sown. This is common in the following families: Araliaceae, Ranunculaceae, Ericaceae, Primulaceae, and Apiaceae.

5. Internal Dormancy

A number of types of dormancy where germination is controlled by the internal condition of the seed. The most significant example is moist chilling, where the seed needs to go through a period of cold before it will germinate. This is common in the Rosaceae family.



Correct Conditions for Seed Storage - This needs to be rewritten, it is straight off a website.

When seeds are being stored for short or long periods of time, the two most important variables to control are moisture level and temperature. As the seed moisture content of seeds is lowered, seed life is increased (to a point of around 6% moisture content). As are the two most important variables in successful seed storage. Each 1% reduction in seed moisture content (down to about 6%) doubles seed life. Each 10% reduction in temperature (down to 32 'F) doubles seed life.

Removing moisture from seeds is done by lowering the relative low-humidity of the surrounding air, which can be done by refrigeration or by desiccation. Refrigerated air is both drier and cooler than room air.

Seeds must equilibrate with 65% relative humidity (or less) for 1-year storage, 45% for 2-3 year storage, and 25% for long-term storage (5-6% seed moisture content).

Dry seeds (<14% moisture) can be stored in the freezer; however seeds must be in moisture-proof containers.

In summary, reasonable storage conditions for several seasons can be provided by storing envelopes of fully mature and dry seeds in heavy zip-lock bags in the refrigerator. Longer storage requires more ideal conditions.



The Tetrazolium Test for Seed Viability

In this test, a colourless liquid is imbibed in the seed. This chemical goes through a reaction (reduction) in living tissue and produces a red substance which cannot be diffused ‑hence any living parts of the seed turn red or pink, and any dead parts of the seed remain unchanged. The chemical used is a one percent solution of 2.3.5.‑triphenyl‑tetrazolium chloride (or bromide).

This test is conducted by cutting a seed in half so the embryo can be seen. The seed is then soaked in the solution (at a temperature between 20 and 30 degrees centigrade, for 12hrs in the dark (in some cases 24hrs is needed). The seed is then studied (a hand lens may be necessary). Seeds can be selected at random from a batch and tested to give an indication of overall viability.


ASEXUAL PROPAGATION

Asexual or vegetative propagation involves producing a new plant from only one parent. A part of an existing plant is treated in some way so that it can produce a new plant...ie. asexual propagation involves growing a new plant from a piece of stem, leaf or root (or possibly all three). In asexual propagation, the parent plant and offspring are genetically identical.

The following techniques are used in asexual propagation:

• Runners - Strawberries
• Suckers - Raspberries

Layering

There are several forms of layering:

Tip ... Black raspberry, boysenberry
Simple ... Honeysuckle, filbert, spiraea, rhododendron, magnolia.
Trench ... Apple, pear, filbert, walnut.
Mound or Stool ... Apple stock, cherry stock, currant.
Air Layering ...Ficus, monstera, philodendron, camellia, rhododendron, azalea, holly, magnolia, lilac.
Compound ... Grape, philodendron, wisteria, magnolia , lilac.

Separation

Bulbs .. Hyacinth, lily, narcissus, tulip.
Corms ... Gladiolus, crocus.

Division

Rhizomes .. canna, iris.
Offsets .. leek, pineapple, date.
Tubers .. potato, dahlia.
Crowns .. phlox.

Grafting

This involves taking a section of stem from one plant and attaching it to another plant in such a way that the two will grow together. Grafting enables you to change the variety of an existing plant. (ie: By attaching a variety which you want to an existing root system you can remove the old top and have a plant comprising the roots of one variety and the top of another). Plants which can be grafted include, apples, pear, peach, almond, citrus, avocado, camellia, ash, birch, elm, walnut.

Cuttings

A cutting is a piece of root, stem or leaf which has been treated in a way that stimulates it to grow roots, stems and leaves; hence producing another new plant.

Cutting propagation can be carried out on a very wide variety of plants, and second to seed propagation, it is the most commonly used method of producing new plants. Cutting propagation is most commonly used for shrubs, indoor plants and many herbaceous perennials. As a general rule, it is not as commonly used to propagate most types of trees.

• Root cuttings Albizzia julibrissin, cydonia, apples, some poplars, rhus, liquidambar, wisteria.
• Stem cuttings Hardwood (in Winter) Quince, rose, grape, fig many deciduous plants.  Semi hardwood (in Autumn) Lemon, camellia, holly, grevillea, azalea, many woody shrubs.
• Herbaceous Geranium, coleus, chrysanthemum, many perennials and herbs.
• Leaf cuttings Begonia, sanseviera, african violet, peperomia, gloxinia.
• Leaf bud cuttings Ivy, rhododendron, boysenberry.

Whilst there are different types of cuttings, the majority of cuttings are pieces of stem, often with some leaves left at the top.

Cuttings are usually planted into a mix of materials such as sand, peat moss, perlite, rockwool or vermiculite. Part of the tissue is usually below the surface of the mix, and some exposed above the surface. The cutting then needs to be kept in optimum environmental conditions for that particular plant. Humidity, temperature, light, water and other factors all affect the success of the cutting.

Chemical hormones may be applied to stimulate the formation of either roots, or foliage/shoot growth. Pesticides or disinfectants may be used to reduce the risk of pest and disease outbreaks. Heating may be used to warm the root zone (ie. bottom heat), to encourage faster growth of roots; or periodic misting of the foliage to cool the top of the plant, or prevent dehydration of the foliage.

Aseptic Micro Propagation (Tissue Culture)

Small sections of plants are grown in the laboratory. As they grow they can be transplanted to individual containers and eventually into soil containers. Also known as tissue culture, this technique is becoming increasingly important in commercial nurseries.

Tissue culture is basically growing plants from either single cells or from small pieces of plant tissue. It involves multiplying plants under sterile, laboratory conditions. Very roughly speaking, a section of a plant is placed in a nutrient environment (eg. a jelly impregnated with the nutrients which are essential to plant growth) and then left in a pathogen-free environment where conditions such as temperature, moisture and light are controlled. After a period of time the microscopic section of plant will grow. Eventually it can be moved (via a series of stages) into the outside environment.

Tissue culture is of increasing importance in the nursery industry. Its commercial potential has rapidly developed over the last two decades, and now many plants sold in nurseries are propagated using this technique. Some plants are much easier to produce by tissue culture than others.

The main advantages of tissue culture are:

• Propagation of difficult species. Some things which have proven extremely difficult to grow other ways have been able to be grown in large quantities only by using tissue culture.
• Plants can be propagated at any time of the year using tissue culture techniques.
• Ability to propagate rapidly. In a situation where a new hybrid has been developed, it can take several years to produce enough individual plants of that hybrid to be able to make it worthwhile marketing it. Using tissue culture it is possible to produce tens of thousands of specimens of the new hybrid within the space of one year. In woody species, breeding and selection by sexual hybridisation has been slow because of the long periods of time between each generation. Tissue culture can speed this process considerably.
• Considerable savings in time and space compared with that required by conventional procedures.
• Disease tested material can be bulked in large quantities without the costly precautions that are otherwise needed to prevent re-infection during propagation. Plants such as lilies, strawberries and potatoes, while not necessarily difficult to propagate conventionally, are very susceptible to viruses.

The above advantages can be offset by problems inherent in the tissue culture method. These include:

• Plants need to be hardened off slowly under high shade and high humidity (misting) conditions, then gradually eased out into normal conditions.
• On planting out you can sometimes get:

1. abnormal or no root growth
2. plants prone to dry out quickly
3. reduced photosynthetic activity of the propagation was done in a sugar enriched environment
4. sometimes an induced dormancy

Only a relatively small proportion of plant species can be cultured well enough to be effectively propagated. The time and expense in developing the required technology may not be worthwhile for minor species. Even when it has been developed scientifically for a particular species, it is often not taken up commercially.

Compared with a conventional propagating bench, a tissue culture laboratory requires a large capital investment with correspondingly higher running costs. Labour is the largest single item of expenditure.

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