A mature grapevine is easily identified by its fruit. But when grapevines are immature, identifying them requires some information on their growth habits and characteristic features. Grapevines always wrap themselves around something, whether it's a tree trunk or a post of some sort. They only grow upward, never outward and never trailing along the ground. With this information and knowledge of some characteristics of the plant's leaves you will be able to identify grapevines.
Look at the shape of the leaves. Grapevine leaves are heart-shaped with three lobes. The edges are always jagged, which can look finely serrated or deeply cut. The leaves can be up to 8 inches across.
Check the colour of the leaves. During the growing season, grapevine leaves can be light to medium green, depending on the type. The colour is uniform throughout the leaves. In winter, as the leaves go dormant, they curl in on the edges and turn a dark purple, almost brown colour.
Look at the underside of the leaves. A white-coloured fuzz grows over the surface of the leaves and down to the stem. There will be curly tendrils, which may be lighter in colour on younger vines. This is a distinguishing feature of grapevine leaves.
Examine the veining in the leaf. Grapevine leaves have very close veins that are straight. They should run evenly through the leaf's surface.
Look for flowers. During the summer, before the vine produces fruit, small white flowers appear in clusters. These flowers are very fragrant.
Examine grapevine leaves at different times of year to be sure of identification.
Various pests may feed on the grapevine's fruit and foliage.