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Riverbank grape's flowers develop in 5" long, drooping, cylindrical or pyramidal panicles opposite the leaves of new branches (but skipping every third leaf). The flowers are greenish-yellow and are best described as skeletal; they may be either unisexual or (rarely) perfect (both male and female reproductive organs functional). The male and female unisexual flowers usually both occur on the same plant, either in separate or mixed clusters; both male and female flowers are 1/8" across or less, with a minute calyx and five green to yellowish petals that quickly fall off. Male flowers have five very long, pale, erect stamens around a button-like center; female flowers have an ovary with a short style and five short, sterile stamens, often contorted. The fruit are .... grapes — a round berry, 1/4-1/2" across containing 1-4 seeds, initially green but turning blue-black as it matures, often with a white bloom on the skin. You know, grapes. The fruit of riverside grape is often sour until after a frost, then becomes more "sweet/tart" to the tongue. Riverside grape is subject to parasitism by the grape filbert gall midge (Ampelomyia vitiscoryloides), an insect whose larvae produce large, very hairy, conical galls at leaf nodes. This gall midge is restricted to the eastern half of North America; it was first described by Alpheus Spring Packard, Jr. in 1869.

Vitis

Vitis riparia

riverbank grape [Blooms: [May-Jun]