Techniques of Plant Propagation

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Chapter 14

• Techniques of Plant Propagation

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• Among all the crafts of ornamental horticulture,
  none exemplifies the application of science to
  the profession better than plant propagation.

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• To promote the initiation and development of new
  roots on cuttings it is necessary to create an
  environment for the cutting base that will
• Support the cutting
• Retain moisture uniformly
• Drain away excess water uniformly
• Provide adequate aeration
• Not support weed seeds and other pests
• Pasteurize easily

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• Materials that can be used in the propagation
  medium
• Natural soil
• Sand
• Peat moss
• Sphagnum moss
• perlite
• Vermiculite
• Fired clay

Peat moss
Perlite
Fired clay
Vermiculite
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• Steam pasteurization is used to eliminate weeds
  seeds, nematodes, fungi, and other soil-borne
  plant pathogens.
• Sand or peat moss are often added to the growing
  medium to improve texture, moisture retention,
  and drainage.

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• The propagation structure must possess the
  following characteristics
• Sufficient light to permit seed germination.
• High humidity to reduce wilting of the cutting
  until new roots can form and promote.
• Warmth to accelerate germination or rooting.
• Ventilation to reduce risk of disease once roots
  have been formed.
• Certain areas of the greenhouse should be
  designated as propagation only because it
  requires higher temperatures and higher humidity
  than typical greenhouse crops.

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• Seed suppliers usually provide the buyer with
  information about the best time to plant, any
  necessary treatments, and follow-up culture
  information.
• Scarification is a process that breaks down tough
  seed coats by rubbing them with sandpaper,
  soaking them in hot water or acid, or by a
  similar process.
• Common Scarification techniques
• Sandpaper
• Hot water bath
• Sulfuric acid bath

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• Stratification- subjecting seeds to a required
  period of low temperatures to induce growth.
• Double dormancy- when plants require both
  scarification and stratification before they
  germinate.
• Factors of good propagation
• Good quality seed
• Correct propagation medium
• Correct planting technique
• Appropriate lighting
• Proper watering
• Good drainage
• Proper temperature
• Adequate nutrients

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• Planting techniques vary depending on whether
  they are herbaceous or woody, and whether they
  are to be transplanted or grown at the planting
  site after germination.
• Plugs are seedlings that retain their undisturbed
  root system within a core of media.
• In the production of ornamentals plugs are mostly
  used for bedding plants.

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• The majority of growers prefer to use plugs over
  seed propagation techniques because
• Transplant shock and transplant times are reduced
• Plugs do not overcrowd as quickly and can be held
  longer for transplant.
• Seed sowing can be automated and there is no need
  to thin the seedlings after germination.
• Plugs can be transplanted automatically.
• Shorter production time allows more crops to be
  produced.
• If plugs are kept too long in a growth chamber
  they will stretch and overgrow.

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• Cuttings are pieces of roots, leaves, or stems
  that are removed from the parent plant and placed
  in an environment that promotes their development
  into total plants.
• Adventitious roots are initiated in herbaceous
  plants from points just outside or between
  vascular bundles. In woody plants they originate
  next to and out from the vascular core. This is
  significant in the cutting process because they
  may form after cuttings are taken or may be
  performed but dormant.
• The best cuttings result from healthy stock
  plants that contain adequate nitrogen and high
  carbohydrate levels.

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• Adventitious roots form more quickly on stem
  cutting in the dark than in the light.
• Stem or root cuttings taken from young plants
  root more quickly than cuttings taken from older
  plants.
• When a species is difficult to root, better
  results are usually obtained when vegetative
  growth is selected for the cuttings.

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• Factors the propagator must consider to protect
  cuttings
• Moisture helps rootless cuttings absorb water.
  Usually created through a mist line.
• Temperature controls the rate of root and shoot
  development.
• Nutrition influences the quality of cuttings
• Acidity/Alkalinity affects the number and
  quality of cuttings.
• Light quality and intensity high light
  intensity is important for good root production.
• Oxygen content oxygen is important for
  developing plants.

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• Hardening-off is important because the gradual
  adaptation of plants to environmental conditions
  are more stressful than the present conditions.
• Plant graft the union of parts from two or more
  plants into a single plant.
• Much of the research into grafting has been
  accomplished with citrus and fruit trees.
• While grafting can be done on both woody and
  herbaceous plants, it is most common to woody
  plants.

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• When the graft union is successful and the two
  different plants become one, it is termed a
  compatible graft.
• Delayed incompatibility a graft may be
  successful for years before suddenly failing.
• Basic items required for grafting
• A knife
• Tying materials
• Grafting wax

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• Budding is grafting using a single bud as the
  scion. To bud a plant, you remove a piece of bark
  and replace it with a similarly sized piece of
  bark from another plant.
• Layering allows a new plant to form by creating a
  new plant that is still attached to the parent
  plant by a stem, and is sometimes the chosen
  method because a new plant can be separated after
  a root system develops.
• Compared to other methods of propagation,
  layering is usually slower, more expensive, and
  produces fewer plants per parent plant.

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Layering
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• Simple layering a dormant one year branch is
  bent to the ground and covered with soil
  excepting the tip. Roots will begin to form in
  the underground segment.
• Tip layering a shoot from current growth is
  bent and covered.
• Mound layering the parent plant is cut back to
  ground level to encourage shoot growth. The new
  shoots are covered with soil. Each shoot makes a
  new plant.
• Air layering a young portion of stem is cut to
  induce root formation. Sphagnum moss is wrapped
  around the injured area, fastened on, and tied.
  When roots form, the new plant is cut from the
  parent.
• Serpentine layering the branch being layered is
  buries in many places, rising above the ground at
  varying intervals.

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• The twentieth century lead the beginning of new
  propagation techniques known as tissue and organ
  culturing. These techniques permit the
  reproduction of certain species from embryos,
  pollen grains, shoots tips, or undifferentiated
  plant tissue.
• Totally sterile or aseptic conditions are
  essential throughout the tissue and organ
  culturing process.
• Tissue and organ culturing are comparatively new
  propagation techniques.

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