Do All Vines Have Trunks?

Types of Vines

• Vine stems are loosely defined as either woody, semi-woody or herbaceous. Herbaceous vines have green, flexible stems that usually die back to the ground in the winter. Woody stems are covered with bark. Semi-woody stems are stiff enough to support the plant but do not contain true wood, according to the University of Miami Department of Biology. Vines with woody stems contain wood and are covered with bark. These stems are structurally the same as tree trunks, but with one important difference that exemplifies why they are not usually called trunks.

Trunks vs. Stems

• The primary difference between a woody vine's stem and a trunk, according to Utah State University Cooperative Extension, is that the woody vine's stem can't support the vine. A tree's trunk, on the other hand, supports the rest of the tree. Vines -- woody and herbaceous -- need a support structure, which may be a fence, trellis, the trunk of a tree, or even the ground.

Main Shoot

• The main shoot of a woody vine is usually trained to grow along a support structure. All stems, including vine stems, start out as herbaceous, which allows them to be trained to grow along the structure. Once they develop bark and become rigid, main woody shoots are difficult to remove from the support structure or transplant. The arms, or branches of the vine sprout from this main stem and are often pruned back to the stem.

Selected Woody Vines

• Wisterias (Wisteria spp.) are an example of a woody vine that has a trunk-like stem. These large, heavy vines thrive in U.S. Department of Agriculture plant hardiness zones 4 through 9. Very old wisterias can have main stems as thick as the trunk of a small tree, according to Sunset. In the case of grapevines, which are hardy in U.S. Department of Agriculture plant hardiness zones 6 through 9, the main stem, which is usually called a trunk, is trained to grow vertically and attached to a trellis. The arms that sprout from the trunk grow horizontally along the trellis. Mature grapevine trunks are usually considered permanently placed.