Photo by John Nelson There are vines and then there are lianas. A vine, in the everyday garden sense, is an herbaceous or soft- stemmed plant that lasts only a year and has elongated stems, either flat on the ground or climbing up a support.

Morning glories and sweet- peas grow as vines, and so do watermelons. But a liana is woody and lasts for many years. Lianas, if given the opportunity, may attain considerable size in both length and girth, and many of them climb up supports.

In forested situations, there tend to be plenty of supports in the forms of trees. If you go into a forest with lots of lianas, you will almost surely notice some big, old ones, much too large and heavy to climb into a tree all the way to its canopy.

Lianas, like most other plants, grow in length only at their tips. So it is only the farthest end of the liana that is actually climbing. The enlarged, massive base of a woody vine isn't growing except in girth. Thus, any large vine you may see growing up a tree has hitched a ride years earlier while the tree was small. Many of the large lianas at the base of an old tree are just about as old as that tree itself.

The lianas looks like a grapevine. Although it is a member of the grape family, it is definitely not a true grape. This species grows in thickets and various woodsy settings from Virginia to Nebraska and south to northern Florida. It's a liana, and its young growth features prominent tendrils, which are good at holding onto a support.

Its deciduous leaves are handsome, smooth, and bright green with saw- tooth margins and a blade base that is usually flat or heart- shaped. The leaves resemble those of the common muscadine, which is a native grape species.

Flowers of the Mystery Plant are held in flattened clusters on a stalk next to a leaf on the other side of the branch. The flowers are inconsequential, but the resulting fruits, which are berries, are quite beautiful. They start out green but mature through a series of colors including pink, red or orange, finally becoming a shiny blue. Sometimes, a sort of porcelain- looking robin's egg blue.

The Mystery Plant is one of those native vines, which probably should be used more in cultivation. The foliage and fruits are very impressive, and birds and critters eat the berries.