Desert Grape

Desert grape (Vitis girdiana) is one of the few woody vines native to the Reserve, and it is unquestionably our biggest. Like other vines, desert grape has given up the stout trunk and branches that give other plants self-sufficiency, and instead it depends upon its neighbors for support. Replacing the sturdy trunk, is a long, slim, flexible stem that grows quickly, lifting its leaves into the sunshine above the surrounding tree canopy.

Years ago, our Rangers planted a few wild grape plants near the La Orilla trailhead as a part of a revegetation effort. The grapes flourished, climbing nearby trees and arching over the trail. Today they make a cool green tunnel through a hot summer afternoon. In autumn the vines rain gold.

Description ^{2,4,11,59,306}

Desert grape is a winter-deciduous perennial vine that forms dense, tangled thickets sprawling along the ground and over shrubs and young trees; grape vines can reach significant distances up the trunks of large sycamores and cottonwoods. The vines climb by means of forked tendrils arising opposite the leaves; these twine around and cling to adjacent structures. Shoots and young leaves are densely covered with white hairs and stand out silvery against the green leaves. The leaves are generally six inches (16 cm) or less in length, rounded to heart-shaped, occasionally with three to five broad shallow palmate lobes. The margins are coarsely toothed. Leaves turn gold and orange in the autumn before they drop.

Tiny flowers occur in dangling, branched clusters that develop opposite a leaf, replacing a tendril. Flowers of different sexes occur in separate clusters on the same plant. On both sexes, the calyx is reduced to a narrow rim, green, aging reddish. The corolla consists of five to seven greenish petals initially forming a cap over the reproductive parts; petals are fused at the tips and split open from their bases, falling entirely from the flower as a unit when the flower opens. Male flowers consist of five to seven stamens in a spray. The pistil does not develop and appears as a small central dome surrounded by a nectary disk. Pistillate flowers consists of a pistil with one superior, ovoid ovary with a short style and a small, two-lobed stigma. [Note: Prigge and Gibson⁴ report viable pollen from pistillate flowers and refer to them as bisexual.] Desert grape flowers from May into June.

The fruit, or grape, is a 1-4 seeded berry, about 1/4 inch long, green maturing purple-black with purple pulp.

Classification ^2,59,143,306

Desert grape belongs to the grape family (Vitaceae), a family of climbing vines with tendrils and distinctive clusters of berries (grapes). The petals are often united at their tips, dropping from the flower as a unit when the flower opens. In addition to the other species of grapes, the ornamental Virginia creeper (Parthenocissus quinquefolia) is a member of this family. Desert grape is the only member of this family in the Reserve.

There are two species of grape native to California. Desert grape and California grape (Vitis californica) are similar in appearance and hybridize in the field. Hybridization with V. arizonica, native to Nevada, Arizona, Utah and Texa,s occurs in a region of overlap near the California/Nevada border. Also, hybridization with the non-native wine grape (V. vinifera) is probable. This interbreeding making identification of some specimens of grape confusing and obscurs the geographic boundaries.³⁰⁶

Ecology ^433,434

Plants in riparian forests must either be shade-adapted or compete with their neighbors for sunlight. Most trees produce woody support structures – trunks and branches – that lift their leaves above the surrounding vegetation into the sunlight.  However, these woody structures require energy to produce and maintain, energy that must be diverted from photosynthesis and reproduction. A significant number of species have developed a vining strategy, forgoing their own support tissue and using surrounding plants as support. This allows them to grow very fast and gives them slim, flexible stems that will bend, twist and stretch rather than break. Vines have several types of climbing gear: the stems may twine around the support like wisteria (Wisteria spp.), tendrils may grab and hang onto smaller branches and twigs, like wild cucumber (Marah macrocarpa) and ropevine clematis (Clematis pauciflora), downward pointing hairs may cling like Velcro, like fiesta flower (Pholistoma auritum); in some cases special structures have adhesive pads that glue them in place, like Boston ivy (Parthenocissus tricuspidata).

Desert grape is the largest vine in the Reserve and it clings by means of forked tendrils from the stem, pulling itself up surrounding shrubs and trees. This allows it to raise its leaves high above the willows, mulefat and sapling sycamores that surround it.

A dominance of vines in an area, has ecological consequences for the surrounding system. Vines overgrow and suppress, even kill, smaller or slower growing plants. On the other hand, they benefit the wildlife by providing arboreal habitats and corridors not present before, and by replacing original food sources with a new one. Desert grapes are especially useful for wildlife. Whether the net change is good or bad, depends upon the goals and aesthetics of the observer.

Human Uses ^15,17,282

A Chumash legend teaches:

The bear knows that if he eats too much of this fruit
it will ferment in his insides and cause him to become intoxicated.
For this reason, the bear has respect for the wild grape.

The local native Americans used the fruit of desert grape as food, either fresh, dried or cooked. The Cahuilla also used them for wine.

Interesting Facts ^41,306,435

In the late 19th Century, a tiny pest called phylloxera nearly destroyed the European wine industry. In this story, North American grape species were both the villains and the heroes.

Phylloxera is a tiny aphid-like insect that feeds on the roots and leaves of grape vines. It is native to North America and native grapes  have evolved defenses to inhibit the phylloxera and restrict its damage. In the late 1800’s, avid Victorian botanists collected North American grapes and brought them to Europe; along with the grapes came phylloxera. It is estimated that  70-90% of the European wineries, especially in France, lost their vines.

Even today, there is no known cure for phylloxera. Initially, several solutions were tried involving hybridization with and grafting to the resistant North American grape vines. Ultimately, it was root-grafting that allowed the recovery of wineries world-wide and the native grapes of North America continue to play a tasteless but pivotal role in wine making.