Vitis riparia Michx, also commonly known as River Bank Grape or Frost Grape, is a native American climbing or trailing vine, widely distributed from Quebec to Texas, and Montana to New England. It is long-lived and capable of reaching into the upper canopy of the tallest trees. It produces dark fruit that are appealing to both birds and people, and has been used extensively in commercial viticulture as grafted rootstock and in hybrid grape breeding programs.
The inflorescence is paniculate 4–15 cm (1.5–6 in) long and loose, and the flowers are small, fragrant, dioecious, and white or greenish in color. V. riparia blooms in May or June and produces a small 6–15 mm blue-black berry (grape) with a bloom, seeded, juicy, edible, vinous in flavor, lacking the "foxy" characteristics of Vitis labrusca, but usually quite sour and herbaceous. V. riparia has a wide range and may deviate considerably in detail from the above general description. White berries, perfect flowers, large clusters, large berries, and sweet fruit are among the known variations. However, some observers consider such variations as evidence of natural hybridization with other species of grapes.
In the wild, the vine thrives along exposed areas with good sun exposure and adequate soil moisture, such as riverbanks, forest clearings, fence lines and along road sides. The species has adapted to a variety of soil chemistries.
Due to the extensive cold hardiness and fungal disease resistance of this species, it has been used extensively in grape breeding programs to transfer cold hardy and disease resistant genes to domesticated grapes. The French-American hybrid grapes are notable examples of these attempts. V. riparia has been used extensively for over a hundred years to create hardy hybrids. Many V. riparia hybrids are currently being used and investigated by plant breeders and in breeding programs such as those conducted by the University of Minnesota's horticulture program in an effort to make a commercially viable wine grape that can survive the northern climate of the Upper Midwest. Examples of commercially important cultivars with significant V. Riparia ancestry include Baco noir, Marechal Foch, and Frontenac.
While V. riparia shares many important characteristics with its cousin, Vitis vinifera, the small size of the berry (making it prone to predation by birds), the high acidity of its fruit (often up to 5% titratable acidity), the intense pigment of its juice, and the presence of herbaceous aromas in wine produced from it have made it unusable on its own for commercial viticulture.