Listen, and understand! Dioscorea polystachya is out there! It can’t be bargained with. It can’t be reasoned with. It doesn’t feel pity, or remorse, or fear. And it absolutely will not stop… ever, until your plants are dead!
Since moving in to our house we’ve dealt with a typical array of weeds and invasives. Plenty of English Ivy. Japanese stiltgrass. Zombie wisteria that keeps coming back no matter what I do. But by far the worst has been Chinese yam, a climbing, strangling vine that is so persistent, I can only assume that a plant in my garden is an ancestor of a key leader of the future plant resistance, so Skynet sent Chinese yam back in time to terminate it.
It doesn’t seem to be one of the most common weeds in our area, but the stuff is pretty much everywhere in our yard, thriving in both sun and shade. It closely resembles bindweed, but the leaves are more rounded and heart-shaped (as opposed to the arrowhead-like bindweed). It starts as a little shoot poking out of the ground, and seemingly within a day it’s grown several feet. You could take a moment to admire a shrub in your yard. Then you go inside for a nice cold drink. When you come back out, you’ll find a new tendril has already made its way to the top of the shrub. Vines seem to seek each other out and wrap around one another to form thick ropes. God forbid you go away for a long weekend. When you get home, you’ll find the ropes have braided themselves together to form an impenetrable blanket over an entire flower bed. The sheer amount of biomass of this species that I’ve removed from my yard so far this spring is incredible. And it’s still everywhere.
As the name suggests, the plant uses tubers to store energy underground. This makes it hard to control. When pulling a vine, if the tubers don’t come up with it, I’ve got some news for you. It’ll be back. And they wind so tightly around their prey, pulling it off just strips the foliage right down to the stem. But the real trouble starts when the vine matures enough to produce aerial tubers in late summer. They look, appropriately enough, like tiny potatoes. And they’re attached to the stems by the most delicate of linkages. So any attempt to pull the vine out at that point will send dozens of tubers flying in every direction, where they’ll lay in wait to sprout a new vine.
This year there seem to be more than ever, and I’m determined to remove as much as I can while making sure any I can’t get to aren’t able to produce new aerial tubers (this happens in late July and August). If the ground is really wet, you can often pull the full plant and tuber from the ground. It also seems like the first sprout from an aerial tuber is a large, kidney shaped leaf, whereas more developed ground tubers (which probably overwintered) will put out a thicker vine to start. The new sprouts are relatively easy to pull from wet soil, especially if you grab a bunch at once. In some areas I can also attack them with a string trimmer without hitting desirable plants. This obviously leaves the tuber behind, but if I keep at it, hopefully it will exhaust all of its underground energy eventually. But a lot of them are around other plants, so it’s pretty much hand-pulling for me.
Either that, or trying to place a healthy plant on the other side of some kind of giant industrial crushing machine, then activating the press just as the vines are creeping through to reach it.