Propagation deals with the deliberate (or intentional) production of new plants using various starter materials (e.g. organs, tissues), including their intensive but temporary care. It is primarily practiced to produce seedlings or clones of nursery crops for outplanting, or for planting in containers for display or decor or other uses.
Nursery crops are those which commonly require the use of pre-grown planting materials for outplanting, or field planting. A plant nursery is the place where seedllings, clones, and potted plants are raised temporarily under intensive care.
The basis of plant propagation is totipotency, the capability of cells to regenerate missing parts and, subsequently, an entire organism. Applied to plants, it means that any live part that is separated from the parent plant, being composed of live cells, can possibly produce missing organs of an intact plant, such as roots and shoot, and give rise to an entire plant. It means that all plant organs with live cells, such as seeds, stems, etc., either intact or segmented, are potential propagules, or propagating materials.
Plant Propagation Methods
Raising from seeds: Germination from seeds may not be 100% even if the seeds are sown in perfect conditions. The factors that control the germination are age, stage of maturity and viability of seeds, water, free supply of oxygen and the heat or temperature. Some seeds do not germinate easily for variety of reasons such as the dormancy, rest period and presence of hard seed coat.
Seeds with hard coats (e.g. palm, cannes, etc.) require some kind of external treatment for germination. Cracking of the coats by mechanical means, abrasion, soaking in water or acid and stratification are some methods commonly applied. Before sowing on a large scale, it is worthwhile to test the viability of the seeds. Eg.: Acid lime, amla, mandarin orange, annona, durian, litchi, mangosteen, West Indian cherry, passion fruit, bilimbi, carambola, karonda, loquat, phalsa etc.
Vegetative Propagation: Safe methods of vegetative propagation such as cutting, layering, division, separation, budding and grafting are adopted for multiplication of ornamental plants.
Cutting: Plant parts that are normally used for this purpose are stems, roots, leaves and modified stems such as tubers, corms and rhizomes, runners and bulbs. This method is very popular, particularly because it is the cheapest and most convenient one. However, in case of annuals, biennials and some perennials, methods such as seedage, layering and grafting are easier and more economical. Eg.: Grapes, pomegranate, pear, West Indian cherry, passion fruit, loquat, phalsa, fig, kiwi, bread fruit etc.
Layering: The method of inducing roots in a stem which is still attached to the plant and then detaching it after the root is formed for transplanting is called a layering or layerage. Mostly creepers and trees are raised by this method. Some herbaceous plants such as carnation, chrysanthemun, etc. can be raised by layering. Eg.: Guava, pomegranate, lemon, West Indian cherry, litchi, karonda, phalsa, rambuton, bread fruit etc.
Division and Separation: The plants which produce masses of stems at ground level, each having its own root system are lifted from ground and divided into individuals. This is called division. In separation, the rooted or unrooted parts usually detach themselves on maturity and start or develop as a new individual in next season.
Plants like chrysanthemum, tube rose, Russelia juncea and most of the herbaceous perennials are easily propagated by division. Bulb hyacinth and crocus are examples of plants that can be propagated by separation.
Suckers, rhizomes, tubers, runners, stolons, bulbs, corms, bulbils, etc., are some other plant parts which are used for vegetative propagation. Eg.: Banana (suckers), pineapple (suckers and slips), straw berry (runners, slips) etc.
Grafting: Grafting, except budding (which is also a form of grafting) is not widely used in ornamental horticulture except in a few cases. The types of grafting which are used in ornamental plants are limited to inarching, side grafting, splice grafting, saddle grafting, flat grafting and cleft grafting.
Inarching is followed in the propagation of roses in some parts of the country. The method of side grafting is followed in case of roses, camellias, etc. Eg.: Amla, mango, sapota, jack, durian, apple, pear, avocado, West Indian cherry, annona, rambuton, persimmon, apricot, loquat etc.
Budding: In ornamental horticulture, mostly ‘T’-budding or ‘Shield’ budding is employed for propagation. Eg.: Amla, ber, mandarin orange, sweet orange, peach, plum, avocado, litchi, loquat, apricot etc.
Tissue culture: The propagation of orchid through meristem culture was the first commercially successful venture in tissue culture. The principles of tissue culture can be successfully employed in respect of ornamental plants with soft tissues. Quite a large number of ornamental plants are reported to respond to propagation by tissue culture method. Few such plants are gladiolus, carnation, lily, rose, gerbera, anthurium, magnolia, fern, cacti, etc. Propagation of ornamental plants by this method is gaining popularity. Eg.: Banana.