Plant propagation

Groups of horticultural plants

• Trees: woody plants with one main trunk (mango, neem).
• Shrubs: woody plants with many stems from the base (hibiscus, bougainvillea as a shrub).
• Climbers: plants needing support (money plant, grape, bougainvillea when trained).
• Annuals: complete life in one season (marigold, zinnia).
• Perennials: live for many years (rose, chrysanthemum as a herbaceous perennial).

Propagation methods

Sexual (by seed)

Cheap and simple, gives many plants, used for most vegetables, annual flowers, papaya and rootstocks. Seedlings may not be true to type, take longer to bear and may be tall.

Asexual (vegetative)

Gives plants identical to the parent (true to type), earlier bearing, and allows the use of hardy rootstocks.

• Cuttings: a detached piece of stem, root or leaf forms a new plant. Stem cuttings: grape, rose, bougainvillea, sugarcane. Rooting hormones such as IBA help rooting.
• Layering: roots are induced on a stem while it is still attached to the mother plant, then it is cut off. Air layering (gootee) is used in litchi and guava; ground layering in jasmine.
• Budding: a single bud of the desired variety (scion) is inserted into a rootstock. T-budding (shield budding) is common in citrus and rose; patch budding in ber.
• Grafting: a scion with several buds is joined to a rootstock so they grow as one. Mango is propagated by veneer grafting, softwood grafting and inarching (approach grafting); apple by tongue grafting.
• Specialised structures: suckers (banana, pineapple), runners (strawberry), tubers (potato), bulbs (onion), corms (gladiolus), rhizomes (ginger, canna).
• Micropropagation: tissue culture producing many disease-free plants (banana).

For grafting to succeed, the cambium layers of stock and scion must be in close contact, and both must be compatible.

Key points

• Vegetative propagation gives true-to-type plants.
• Air layering (gootee) suits litchi.
• T-budding suits citrus and rose.
• Mango: veneer or softwood grafting, inarching.
• Banana: suckers or tissue culture.

Exam tips

• Expect "match the crop with its propagation method" questions.
• In grafting, cambium contact is the key condition.