1. Techniques of Plant Propagation
Chapter 14
Techniques of Plant Propagation

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

3. 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

4. Materials that can be used in the propagation medium:
Natural soil
Sand
Peat moss
Sphagnum moss
perlite
Vermiculite
Fired clay
Peat moss
Perlite
Vermiculite
Fired clay

5. 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.

6. 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.

7. Common Scarification techniques:
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

8. Factors of good propagation:
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

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. Basic items required for grafting:
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

16. Budding is grafting using a single bud as the scion
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.

17. Layering

18. 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.

19. 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.