Wisteria frutescens (L.) Poir.

American Wisteria

Wisteria frutescens plant

Family - Fabaceae

Stem - To 15 m or more, high-climbing, strongly woody, stout, twining in counterclockwise fashion, unarmed, glabrous or nearly so, tan to brown.

Wisteria_frutescens_stemStem (liana).

Leaves - Alternate, odd-pinnately compound, petiolate, with 7-13 leaflets. Stipules 1-3 mm long, linear, shed early; stipels similar to the stipules, mostly shed early. Leaflets 4-8 cm long, ovate to elliptic, rounded to broadly angled at the base, sharply pointed, the margins entire, the upper surface glabrous, the lower surface and margins hairy, the terminal leaflet with the stalk 10-25 mm long, the lateral leaflets very short-stalked.

Wisteria_frutescens_leafLeaf.

Inflorescence - Terminal racemes, showy and with numerous flowers, to 25 cm long, pendent, the bracts 4-14 mm long, lanceolate, shed early. Flower stalks to 14 mm, densely pubescent with stiff hairs and also club-shaped, stalked glands.

Wisteria_frutescens_inflorescenceInflorescence.

Wisteria_frutescens_pedicelsAxis and flower pedicels.

Flowers - Calyces 6-9 mm long, white to pale green, densely pubescent with stiff, mostly loosely ascending hairs and also scattered club-shaped, stalked glands. Corollas papilionaceous, glabrous, 15-20 mm long, bluish purple, often with a white and/or light yellow region toward the base, the banner with the expanded portion bent backward near midpoint. Stamens 10, 9 of the filaments fused and 1 filament free, the anthers small, attached at or near the base. Ovary 10-12 mm long, linear, short-stalked, encircled by a ringed nectar gland below the midpoint, glabrous, the style glabrous, the stigma terminal.

Wisteria_frutescens_calyxCalyx.

Wisteria_frutescens_flowersCorollas.

Flowering - April - May.

Habitat - Bottomland forests, streambanks, bases of bluffs, former homesteads.

Origin - Native to the U.S.

Other info. - These large, showy inflorescences are hard to miss, and the plant has often been used as an ornamental, for obvious reasons. Over time the weight of the vegetation can become substantial, so stout trellises must be used for support. The flowers are strongly scented, and floral extracts have been used as a fragrance in soaps, incense, etc. The flowers have been eaten, but the seeds are somewhat toxic and should not be consumed.

The genus name Wisteria is named for Dr. Caspar Wistar (1761-1818) from Philadelphia. Wistar was an intellect who used to throw parties known as "Wistar Parties" for other intellects of the day. Wistar was also an avid botanist. Thomas Nuttall named the genus in his honor. The original spelling of the genus was Wistaria.

Photographs taken at Route 66 State Park, St. Louis County, MO, 5-10-2015 (SRTurner).



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