Silverleaf Grape (Vitis aestivalis bicolor)

Description: This woody climbing vine is up to 25' in length (rarely longer), branching occasionally. By means of its twining tendrils, this vine has the capacity to climb adjacent vegetation and fences. On older vines, the trunk is woody and up to 5" across; the gray to reddish brown bark peels into long shredded strips. Older branches have bark that is similarly colored, but more smooth. Young non-woody branches are light green to bright red; they are terete to angular, glabrous to sparsely hairy, and sometimes glaucous. The pith of branches is brown; at the swollen nodes of the branches, this pith is interrupted by a thin white partition about 2 mm. or more across. Alternate deciduous leaves occur along non-woody branches. Except for every third leaf along the vine, there is a branched tendril or inflorescence that is opposite from each leaf. Individual leaves are 3-8" long and similarly across; they are orbicular to oval with 3 or 5 palmate lobes, while their margins are dentate. The palmate lobes vary from shallow to deep. When the lobes are deep, they form narrow sinuses with rounded bottoms (rather than sharply cleft bottoms). On each vine, at least some leaves will have deep lobes. The upper leaf surface is medium to dark green and hairless, while the lower leaf surface is bright white, hairless, and glaucous. The petioles of the leaves are 3-5" long, rather angular, and usually glabrous.

The greenish yellow flowers are produced in panicles about 2-5" long. These flowers can be either unisexual (male or female) or perfect. Individual flowers are about 1/8" (3 mm.) across, consisting of 5 deciduous petals, an insignificant calyx that has been reduced to a flat disk, and the reproductive organs. Male flowers have 5 prominent stamens, while female flowers have a superior ovary with a short style. Perfect flowers have both types of reproductive organs. The blooming period occurs from late spring to early summer and lasts about 1 week. The flowers are quite fragrant. Fertile female flowers are replaced by berries that are arranged in panicles about 3-8" long. These panicles are usually wider near their bases than toward their tips. After they become mature during late summer or autumn, individual berries are ¼-½" across, globoid in shape, dark blue to black, and slightly glaucous. Each berry has a juicy interior with 1-4 small seeds. The flavor of mature berries varies from sweet to sour.
Distribution Map

Cultivation: This woody vine prefers full to partial sun, mesic to dry-mesic conditions, and soil containing sandy loam or some rocky material. Production of berries is facilitated by exposure to sunlight.

Range & Habitat: The native Silverleaf Grape is occasional in NE Illinois, otherwise it is rare or absent. This map combines the distribution of the more common typical variety, Vitis aestivalis aestivalis (Summer Grape), and Vitis aestivalis bicolor (Silverleaf Grape), as described here. Habitats for Silverleaf Grape include upland sandy woodlands, rocky open woodlands, sandy savannas, openings in sandy woodlands, woodland borders, sandy thickets, areas along woodland paths, slopes of sandy bluffs, and roadsides. In these habitats, oak trees (especially Black Oak) are the dominant canopy trees. Silverleaf Grape is more common in areas where there has been occasional wildfires and other kinds of disturbance.

Faunal Associations: The flowers are cross-pollinated by bumblebees (Bombus spp.), honey bees (Apis mellifera), and probably other long-tongued bees (see Robertson, 1929). In addition to these floral visitors, many insects feed on the foliage and other parts of Silverleaf Grape and other wild grapes. These species include Daktulasphaira vitifoliae (Grape Phylloxera), which forms galls on the leaves and roots; Cecidomyia viticola (Grape Gall Midge) and Lasioptera vitis (Grapevine Tomato Gall Midge), which form galls on the leaves or tendrils; the caterpillars of Alypia octomaculata (Eight-Spotted Forester), Harrisina americana (Grapeleaf Skeletonizer), Vitcacea polistiformis (Grape Root Borer Moth), and many other moths (see Moth Table); the plant bugs Paraxenetus guttulatus and Taedia scrupea; the aphid Aphis illinoisensis, which sucks juices from new leaves and shoots; many Erythroneura spp. and other leafhoppers, which suck juices from the foliage (see Leafhopper Table); Heterothrips vitis (Grape-Bud Thrips) and Drepanothrips reuteri (Grape Thrips); Anomala lucicola (Light-Loving Grapevine Beetle) and Pelidnota punctata (Spotted Grapevine Beetle), which feed on the foliage; larvae of the long-horned beetles Clytoleptus albofasciatus (Grape Trunk Borer) and Saperda puncticollis (Woodbine Borer), which bore through the wood of dead and dying vines; and Megaphasma denticrus (Giant Walkingstick), which feeds on the foliage. The Insect Table has a more complete list of these species.

Silverleaf Grape and other wild grapes are also valuable to various vertebrate animals. The berries are eaten by the Ruffed Grouse, Wild Turkey, Cardinal, Scarlet Tanager, Cedar Waxwing, Pine Warbler, and many other birds (see Bird Table). Many mammals also eat the fruit; these species include the Black Bear, Coyote, Red Fox, Gray Fox, Fox Squirrel, Gray Squirrel, Raccoon, Opossum, and Striped Skunk. These animals help to spread the seeds into new areas. The White-Tailed Deer and Cottontail Rabbit browse on the foliage. Insectivorous birds benefit from wild grapes indirectly because of the large number of insects that are attracted to the vines. Some species of birds like to nest in the cover that is provided by the tangled vines of wild grapes, and sometimes they use the shaggy strips of bark in the construction of their nests. In addition to nesting habitat, Wild grapes provide excellent cover for many other kinds of animals.

Photographic Location: A sandy savanna at Indiana Dunes State Park in NW Indiana.

Comments: Silverleaf Grape is the only native wild grape in Illinois with leaf undersides that are bright white, hairless, and glaucous. The more common typical variety, Vitis aestivalis aestivalis (Summer Grape), has leaf undersides with appressed woolly hairs. In form, the leaves of Silverleaf Grape resemble those of Vitis palmata (Catbird Grape), which is restricted to southern Illinois. Catbird Grape, however, has leaf undersides that are light green and glabrous; they are never bright white and glaucous. Another native species, Vitis cinerea (Winter Grape), often has leaves with bright white undersides. However, this is the result of fine woolly hairs that are bright white. Unlike Silverleaf Grape, Winter Grape never has deeply lobed leaves. Another scientific name of Silverleaf Grape, Vitis aestivalis argentifolia, is sometimes used, but it is a junior synonym. Silverleaf Grape was originally regarded as a distinct species, Vitis bicolor.