propagation of plants is effected in nature chiefly sexually by the seed and the spore, less often by rhizomes and other methods (see reproduction). Vegetative means include cutting, layering, grafting, tissue culture, and division of the roots (see perennial) and of the tubers (see potato). Most farm and garden crops are propagated by seed, but some plants will not breed true from seed and must be propagated by various vegetative methods, depending on the type of plant.
See M. A. Dirr and C. W. Heuser, The Reference Manual of Woody Plant Propagation (1987); S. Bittman, Seeds (1989); H. T. Hartmann and D. E. Kester, Plant Propagation (5th ed. 1990).