Culture
Best grown in acidic, moderately fertile, medium moisture, well-drained soils in full sun. Best flowering in full sun. Needs a sturdy support structure on which to grow. Can be invasive (rampant growth plus rooting surface runners). Needs regular pruning to control size and shape of plant. Can be slow to establish.
Noteworthy Characteristics
Wisteria floribunda, commonly called Japanese wisteria, is a woody, clockwise-twining, deciduous vine which typically grows 10-25' (sometimes larger). Can also be trained as a multi-stemmed shrub or small tree. Features bright green, 12-16" long, compound pinnate leaves (each with 15-19 leaflets) and 1.5-3' long drooping clusters (racemes) of fragrant, pea-like, blue to violet, pink or white flowers which bloom from the base of each cluster to the tip in May as the leaves emerge. Flowers give way to pendant, velvety, bean-like seed pods (to 6" long) which ripen in autumn and may persist into winter.
Genus name honors Caspar Wistar (1761-1818), professor of anatomy at the University of Pennsylvania.
Specific epithet means free-flowering or producing abundant flowers.
'Rosea' has pale rose-pink-tipped-purple flowers.
Problems
Though susceptible to a number of foliage-chewing insects and fungal diseases, none are significant. Considered a high maintenance plant, however, because of its need for regular pruning, its invasive tendencies which must be constantly monitored (particularly if grown on structures adjacent to buildings) and its vulnerability to late spring frost damage to flower buds.
Uses
Excellent vine for large, sturdy, free-standing arbors, pergolas or fences. Can be grown up the side of buildings on large trellises or other structures. May be trained as a specimen shrub or tree.