Riverbank grape is the most widespread of the native North American vines, and its range extends quite far north. In the wild it grows on river banks, as the common name indicates, but also in forest openings and along roadsides, either clinging onto other plants or growing along the ground. The alternative common name of frost grape doesn’t refer to its hardiness, but to the sweetening effect of the first frosts on the grapes. In America these acid but aromatic wild grapes are still picked for home-made juices and jams.
Even more important than their use in juices and jams, this species has been used as root stock for less hardy grape varieties. Crossings of the riverbank grape with the true grape (V. vinifera) and other wild grapes has produced varieties which can be grown under conditions where the true grapes don’t thrive. In Finland, for example, the varieties ‘Beta’ and ‘Valiant’ can be grown successfully. They are hybrids of riverbank and fox grape (V. labrusca). However, even these varieties only produce ripe fruits out of doors in the warmest spots, and perhaps not every year; in the protection of even an unheated greenhouse crops are more reliable.
At Mustila there are riverbank grapes of very northern natural provenances, which are hardier than the varieties. Although the forest-like conditions at the Arboretum are perhaps not the ideal setting, some varieties have also been planted against warm walls in the hope of fruiting.