Knotweed seeds, Mame's

In the archives of botanical public enemies, the Japanese Knotweed is pretty close to the top of the worst-of-the-worst list. Polygonum cuspidatum is a native of Japan, China, and Korea, and whoever brought it to this country in the 19th century as an ornamental is surely, these days, roasting in Invasive Species Hell. Knotweed forms dense thickets of bamboo-like canes, particularly in wettish ground, and it can out-compete any of our natives in the ongoing battle for habitat space. Worse still, the plant is all but impossible to eradicate, since digging it up only results in making more pieces of the exceeding tough rhizome to propagate. As if that weren't enough, there are all those seeds, winged and light enough to catch November breezes and so travel to new areas. Still, those negative attributes aside, you can kind of see why someone thought P. cuspidatum belonged in our gardens. It's maintenance free, it has reasonably pretty flowers, and the translucent seeds backlit by the mid-autumn sun are definitely a pretty—and photogenic—sight.