Plants are propagated by asexual or sexual means. Sexual propagation involves starting plants from seed, while asexual propagation is the multiplication of plants from vegetative plant parts like shoots, roots, and leaves, or from specialized organs like bulbs and corms.
The most important reason for asexual propagation is to reproduce plants with the same characteristics as the parent plant. Asexual propagation is the only practical means of propagation when:
•No seed are produced (French tarragon, peppermint, seedless grapes).
•Seed are difficult to germinate (Viburnum, honeysuckle).
•Seed of plants often produce variations that are not desirable (roses, most fruit trees).
•You want to combine two or more plants to get the specific benefit of a particular rootstock. For example, you can achieve size control using dwarfing rootstocks as is done for apples. Or you can get pest resistant rootstock, as in grafting European grapes on American grape rootstocks to avoid damage from Phylloxera, a grape root aphid.
A group of plants originating from a single plant and reproduced by vegetative means is called a clone. For example, the Burkwood viburnum is a hybrid which originally came from seed but is propagated by asexual methods to maintain its unique characteristics. Methods of asexual propagation include cuttings, layering, grafting, and division.
