Botany Blueprint: Wisteria
The Japanese Wisteria (and Chinese Wisteria, which is also common — and controversial — in the United States) was introduced in the early 1800s. Its landscaping motif was designed, but, like many introduced species, its integration was not, and containing the wisteria is a challenge that becomes particularly futile once the plant has extended its roots. Spanning up to 40 feet, the root system will produce new growth that opportunistically surges through soil, sidewalk, or a plumbing network. The winding vines are thick and woody, more closely resembling tree trunks. The arms spiral around an established armature, often deeply embedding the supporting bark or fracturing an architectural infrastructure. Accurately blamed for the demise of plants and porches alike, it’s meanwhile adored for the long flourishes of blossoms — and, among a narrower demographic, for its seed pods.
In front of my house is a spiral of wisteria and fig (the latter the host and also a strong-willed plant). It’s a spectacle of botanic heavyweights. When the wisteria bloomed last spring, I waited for the fruits. Light green fingers grew out of the dwindling petals. After several months, the vine was heavy with long velvety pods, hanging steady and still. As some started to brown, others began to split and spiral, mirroring the vine’s course and revealing seeds inside. Dried coils and seeds were already accumulating on the ground when I clipped several of the pods, in various hues of green and brown. Within an hour, I was startled by a sharp pop. One of the pods opened — a delicate reveal at the seams, one that belied the forceful noise. This explosive gesture fits with the wisteria’s strength. It’s a force that builds as the seed pod dries. When the seeds are mature, the accrued tension culminates in a parting of the two walls. The abrupt splitting and curling breaks the binds between seed and carrier, sending the seeds soaring at distances of sometimes seventy feet. According to wisteria seed pod enthusiasts, the best seat of the season, particularly on a hot day, is directly under the canopy, where you can enjoy a musical score of sharp cracks and subsequent patters as the seeds ricochet off adjacent surfaces and slide along the sidewalk.
The seeds are relatively large and poisonous, which fits with the plant’s dissemination strategy. It grows best in riparian habitats and prefers to travel by water, rather than in an animal’s large intestine. If the riverside option isn’t available, though, no matter. The underground lattice of tenacious roots can be depended on for new growth, sweeping purple boughs, and noisy seed cases.