Wisteria can be seen in several places at Longwood Gardens, and visitors often comment on these growing along the outside conservatory balcony of the Peirce–du Pont House. The blooms are spectacular, but they appear early in spring and only last for a short time—about two weeks in early May, and some years it rains for those two weeks. I took this photo a few years ago on a visit just for that purpose. It was a sunny day, and I knew the wisteria was in full bloom. If I waited, they could all be gone.
After the blooms are over, the vines are covered with dangling seed pods that resemble melting lima bean pods. These pods provide interest over most of the winter, and then one day they are gone. I thought that was all there was to it.
Recently, just a few weeks ago, a Longwood gardener was on a cherry-picker trimming back the vines. He said we could hear the pods bursting open. Sure enough, once he mentioned it, I became aware of the constant snapping. He said they were popping early this year, probably because of the dry weather.
As the pods dry on the vine, they twist (here, clockwise, indicating they are a Japanese variety), and this increasing strain eventually causes them to suddenly burst open, flinging the seeds outward. I then noticed the black seeds, also about the size of lima beans, and the dried, twisted pod remains scattered over the paved areas. They were still raining down as I looked.
The seeds sprout like a lima bean. Two fibrils emerge from the seed and grow in opposite directions. One is the stem and grows upward. The other is the root and pushes downward into the soil.
All of the wisteria plant is poisonous, especially the seeds and pods. As few as two seeds can kill a child. The Longwood staff quickly sweeps them up. The seeds are very bitter, and household pets, like the late Belin the Cat at Longwood, avoid them. Children usually quickly spit them out and are unlikely to swallow one, let alone another.
The gardener I was talking with thought of the seeds as a nuisance because they fell into the pachysandra, and he would eventually have to pull up the sprouts. Homeowners are often overwhelmed by the plant’s aggressive growth that grabs anything it can wrap around, and the beautiful but poisonous vine becomes seen as a voracious evil weed with murder in its heart. Better you should plant poison ivy. Or bamboo. Or forget the hassle of growing them altogether and just visit Longwood Gardens to see them. The new season of blooms will soon start, especially with this mild weather. But hesitate and you will miss them.
Note 4/17: I had picked up a few of the seeds at Longwood and poked them into the dirt in a window flowerpot, thinking the plants would make a nice souvenir. They quickly sprouted, and within a few weeks I had sturdy young plants, each now in its own pot. Thus encouraged, I looked up their care on Google. I quickly learned that wisteria grown from seed takes about 15 years to bloom, and that ended that project. I can’t bare to throw them out, so I will probably plant them along a back fence as a gift to a future owner. I will never see the results.