A vine in the narrowest sense is the grapevine (Vitis), and more generally, any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word also can refer to such stems or runners themselves, for instance when used in wicker work.
In the United Kingdom, the term "vine" applies almost exclusively to the grapevine. The term "climber" is used for all climbing plants.
Certain plants always grow as vines, while a few grow as vines only part of the time. For instance, Poison Ivy and Bittersweet can grow as low shrubs when support is not available, but will become vines when support is available.
A vine displays a growth form based on long stems. This has two purposes. A vine may use rock exposures, other plants, or other supports for growth rather than investing energy in a lot of supportive tissue, enabling the plant to reach sunlight with a minimum investment of energy. This has been a highly successful growth form for plants such as Kudzu and Japanese Honeysuckle, both of which are invasive exotics in parts of North America. There are some tropical vines that develop skototropism, and grow away from the light, a type of negative phototropism. Growth away from light allows the vine to reach a tree trunk, which it can then climb to brighter regions.
The vine growth form may also enable plants to colonize large areas quickly, even without climbing high. This is the case with Periwinkle and Ground Ivy. It is also an adaptation to life in areas where small patches of fertile soil are adjacent to exposed areas with more sunlight but little or no soil. A vine can root in the soil but have most of its leaves in the brighter, exposed area, getting the best of both environments.
The evolution of a climbing habit has been implicated as a key innovation associated with the evolutionary success and diversification of a number of taxonomic groups of plants. It has evolved independently in several plant families, using many different climbing methods such as:
- twining their stems around a support (Morning Glories, Ipomoea species).
- by way of adventitious, clinging roots (Ivi, Hedera species)
- with twining petioles (Clematis species)
- using tendrils, which can be specialized shoots (Vitaceae), leaves (Bignoniaceae), or even inflorescences (Passiflora)
- using tendrils which also produce adhesive pads at the end that attach themselves quite strongly to the support (Parthenocissus)
- using thorns (climbing rose) or other hooked structures, such as hooked branches (Artabotrys hexapetalus)
The Climbing Fetterbush (Pieris phillyreifolia) is a woody shrub-vine which climbs without clinging roots, tendrils, or thorns. It directs its stem into a crevice in the bark of fibrous barked trees (such as bald cypress) where the stem adopts a flattened profile and grows up the tree underneath the host tree's outer bark. The fetterbush then sends out branches that emerge near the top of the tree.
One odd group of vining plants is the fern genus Lygodium, called Climbing Ferns. The stem does not climb, but rather the fronds (leaves) do. The fronds unroll from the tip, and theoretically never stop growing; they can form thickets as they unroll over other plants, rockfaces, and fences.