herbaceous or woody plants, capable of climbing to a greater or lesser height above the ground by twining their stems around a support. This ability makes it possible for twining plants in shady forests or dense stands of grass to send their leaves out in better-illuminated levels. Twining plants wind themselves around the stems of neigh-boring plants thanks to the rotational movement of the tips of their shoots, which results from the more rapid growth of the outer sides of the shoots. The growing point of twining plants moves either to the left, in a counterclockwise direction (in the majority of twining plants, such as beans and bindweed), or to the right (hops); sometimes the direction of the spiral may change (for example, in bittersweet). There are many twining plants in the morning-glory family (Convolvulaceae), milkweed family (Asclepiadaceae), pea family (Papilionaceae), and other families. Some twining plants have devices (protuberances, thorns, coarse hairs) for attaching their stems to the surface of the support (for example, in hops); others have become parasites (for example, dodder).
Twining plants are often erroneously called climbing plants, which climb not by winding around a support but merely by attaching themselves to it by tendrils, hairs, and the like. Both these groups of plants are called lianas. Twining plants are planted along walls, arbors, fences, terraces, windows, and arches and are used in wreath arrangements. Some species of twining plants are used as potted plants to decorate residential, industrial, and other premises. Poles, wire, or twine are used as supports for twining plants. Among twining plants used in ornamental horticulture are grapes, ivy, hops, twining roses, Schisandra, Actinidia, morning glory, scarlet runner, wisteria, honeysuckle, moonseed, sweet peas, and some forms of clematis. Perennial twining plants are propagated mainly by vegetative means, such as division of shrubs, layering, and cuttings. Annuals are raised from seed and from seedlings.