Wisteria

A massive, fast-growing deciduous woody vine from China, famous for its mid-spring curtains of fragrant, lavender-to-violet (sometimes white) pea-like flowers hanging in long, dense racemes that open all at once before the leaves fully expand. The display is genuinely spectacular — but Chinese wisteria is one of the most aggressive ornamental vines in cultivation, and across the southeastern United States it has escaped gardens to become seriously INVASIVE, twining up and GIRDLING trees, smothering whole canopies, and forming dense thickets that crowd out native plants. It is extremely vigorous, twines counterclockwise with great force, and demands very sturdy support, hard annual pruning, and constant vigilance to keep it off houses, gutters, and trees. The seeds and pods are TOXIC if eaten. For most gardeners the honest recommendation is to plant the native American wisteria (Wisteria frutescens) instead — it gives a similar flowering effect with a fraction of the aggression and none of the invasive ecological cost.

Japanese wisteria is a woody deciduous twining climber native to Japan, where it climbs trees and scrambles over woodland margins; it produces the longest flower racemes of any wisteria — pendulous violet, lilac, pink, or white clusters reaching up to 2 m (7 ft) in named cultivars — and a powerful grape-like fragrance in spring. In cultivation it excels as a dramatic focal-point trained over pergolas, arches, or walls, and can become a centenarian specimen. The honest catch is a cluster of serious drawbacks that every gardener must weigh: all parts are toxic (seeds and pods particularly so, a documented cause of poisoning in children and pets); it can take up to a decade to flower from seed; unpruned stems can engulf and structurally damage buildings, trees, and gutters; and it is listed by the Global Invasive Species Database as invasive in parts of North America, Australia, and elsewhere, where it has escaped cultivation and smothers native vegetation.