Description: This is a native woody perennial vine
up to 50' long. It usually climbs trees, shrubs, or fence rows, but will rise
only ½–2' above the ground while sprawling in open areas. The woody
stems branch
occasionally, and can become quite thick with
shaggy bark toward the trunk. The smaller non-woody stems are green or red, and
hairless. At the leaf nodes, these stems become slightly wider, where there is
a thin partition in the pith (about 1/12"). The alternate leaves are up to 6"
long and 4" across, and have long petioles. They are cordate or orbicular in
overall shape, and palmately lobed (although only three lobes may be clearly
visible). The margins are coarsely serrated and slightly ciliate. There are
usually a few white hairs on the underside of each leaf near the major veins,
while the upper surface is glabrous. The small greenish-white or
greenish-yellow flowers have 5 tiny petals, long exerted stamens, and a
fragrant musky scent. Along with the tendrils, they occur in clusters opposite
from the leaves, except every third one. The blooming period occurs during the
late spring and lasts about 2-3 weeks. The flowers are replaced by fruits that
develop during the summer. These are initially small and green, but become 3/8"
across at maturity during late summer or early fall. These mature fruits are
purple or blue with a whitish bloom, each one containing 2-4 seeds. They are
usually sour, even when fully ripened. The root system consists of a central
taproot that branches occasionally.
Cultivation: The preference is full sun to light
shade, and moist to slightly dry conditions. This plant is not particular about
soil texture, which can contain significant amounts of loam, sand, or gravel.
It can be difficult and slow to start plants from seed, so stem cuttings or
transplants are recommended as methods of propagation. Like other wild grapes,
this plant can smother and kill shrubs and small trees.
Range & Habitat: Riverbank Grape occurs in most
of Illinois, except for a few southern counties (see
Distribution
Map). It is occasional to common in most areas. Habitats include moist to
mesic black soil prairies, woodland edges and openings, sandy woodland edges
and openings, savannas and sandy savannas, sand dunes, thickets, areas along
rivers, lakes, and ditches, powerline clearances, fence rows and
abandoned fields, and
areas along roadsides and railroads. In prairie habitats, this plant is usually
near sources of water, woodland borders, or disturbed areas. Recovery from
wildfires is poor.
Faunal
Associations: In general, wild grapes are very valuable as a source
of cover and food to many insects and animals. Bumblebees, small bees and
flower flies visit the flowers, where they seek pollen primarily. The
caterpillars of many moths, particularly Sphinx moths, feed on the foliage and
other parts of this plant (see
Moth Table). Other insects feeding on this
plant include aphids, leafhoppers, beetles, midges, mites, thrips, and scale
insects. Japanese Beetles (Popillia japonica) are particularly fond of
grape foliage, and can cause major damage. The fruit is an important source of
food to some upland gamebirds and many songbirds (see
Bird Table). Several mammals consume the
fruit, including the Black Bear, Gray Fox, Opossum, Raccoon, Striped Skunk,
Spotted Prairie Skunk, and Fox Squirrel. These birds and mammals help to
distribute the seeds far and wide. Occasionally, the Cottontail Rabbit and
White-Tailed Deer browse on the foliage and stems.
Photographic
Location: The upper photograph was taken along a fence row
near the Prospect Cemetery Prairie in Ford County, Illinois. The lower
photograph was taken along a fence row at the webmaster's apartment complex in
Urbana, Illinois.
Comments: This is probably the most common
wild grape in Illinois, and the species most likely to be found in prairie
remnants. Distinguishing different species of wild grape can be difficult.
Riverbank Grape has the following characteristics that together set it apart
from the others: 1) The underside of the leaves are nearly hairless, not
pubescent; 2) the stems are hairless; 3) at the nodes of the leaves, there is a
partition in the pith of the stem that is about 1/12" across; 4) there are no
tendrils nor fruits opposite from every third leaf; 5) the newly emerging
leaves and growing ends of the stems are reddish and nearly glabrous, rather
than whitish and softly pubescent; 6) the fruit usually has a sour taste, even
when mature; 7) the leaves are more coarsely serrated than many other species;
and 8) the plants are more often found in dry, sunny places. The first five
characteristics above are the most important for establishing identification of
species.