Culture
Best grown in slightly acidic, humusy, moderately fertile, moist, well-drained soils in full sun. Full sun is needed for best flowering. Although vines may produce flowers by the second or third year after planting, first flowering may take longer. Vines need regular pruning(s) in order to control size and shape of the plant and to encourage flowering. Consult a pruning guide for specifics on the initial training of vines and the types of pruning that can or should be done for these plants. An application of fertilizer in early spring can also help stimulate flowering. Choose growing sites wisely because plants dislike being transplanted.
Noteworthy Characteristics
Wisteria frutescens, commonly called American wisteria, is a twining, deciduous, woody vine that grows to 40’ or more. It is native primarily to moist thickets, swampy woods, pond peripheries and stream borders from Virginia to Illinois south to Florida and Texas. In Missouri, W. frutescens var. macrostachya is found in the far southeastern bootheel area. Fragrant, pea-like, lilac-purple flowers in drooping racemes to 6” long bloom in April-May after the leaves emerge but before they fully develop. Limited additional summer bloom may occur. Flowers give way to narrow, flattened, smooth seed pods (to 5” long) which ripen in summer. Pods typically split open in fall. Compound, odd-pinnate leaves (each leaf typically with 9-15 lance-shaped leaflets) are deep green. American wisteria is not as aggressive a spreader as Wisteria sinensis (Chinese wisteria).
Genus name honors Caspar Wistar (1761-1818), professor of anatomy at the University of Pennsylvania.
Specific epithet means shrubby or woody.
Problems
Although susceptible to a number of foliage-chewing insects and fungal diseases, none are significant. Failure of vines to produce flowers may be attributable to a number of causes including death of flower buds in winter, too much shade, plants too young (especially seed grown ones), improper pruning or overfertilization. Deer tend to avoid this plant.
Uses
This is an excellent vine for freestanding arbors, pergolas, posts, trellises, fences or terrace walls.