June 2023 Plant of the Month
Wisteria frutescens M(L.) Poir., American wisteria
June’s Plant of the Month is a vine we don’t often associate with a native species. The genus Wisteria was named after Professor Casper Wistar, the inspiration for the Wistar Institute, and a distinguished anatomist from Philadelphia. The genus includes the notorious invasive Chinese and Japanese wisteria, both of which can smother other plants and make the habitat unsuitable for many native species, plants and animals. On the contrary, the native species Wisteria frutescens is not that aggressive. Wisteria is a member of the Bean family, the Fabaceae. It prefers the shade of well drained forests as well as the margins of wetlands. Mary Hough (1983) identified the plant as rare, present from escaped garden plants, and non-persistent. Vouchers specimens where know for Monmouth, Atlantic Cape May and Cumberland Counties. Stone (1910) did not recognize it as a native part of Southern New Jersey’s flora, and Fernald (1950) cited the species on the southeastern coastal plain, reach as far north as southeast Virginia, and escaped elsewhere. USDA (2023) maps the species as a native, with an expanded New Jersey footprint into the northern counties of Warren, Morris, Passaic and Bergen. The species shown in this month’s description is a specimen from Burlington County. It appears this species has slowly entered the state from its southern population, and become an established part of the New Jersey modern, human-modified flora.
Northeastern North America supports three species within this twining shrub genus. The two additional species are Wisteria floribunda, and W. sinensis. American wisteria is a spring flowering vine. It differs from other members of this genus by a few distinct attributes. The flowers are born on short racemes. Similar to Wisteria floribunda, the stems wrap in a counter clockwise fashion. Last, the legumes produced at the end of the season are glabrous, or hairless.
Our Plant of the Month has no known medicinal or food uses (Moerman, 1998). The American wisteria flowers throughout the month of May, but its distinct climbing stems and hairless legumes are features to help identify out of season.