Late August and early September mark the last opportunity to pull Japanese stiltgrass before it goes to seed. An annual grass that was introduced from Asia, and which wildlife show no interest in eating, stiltgrass has taken over large swaths of the forest understory in Princeton, as well as many yards. We called it bamboo grass when we first noticed it in the 1990s, back when I was living in the piedmont of North Carolina. It was also called packing grass, because it had in the past been used to pack porcelain coming from Asia. That's probably how it got a foothold in the U.S.
Many people assume that since stiltgrass is so widespread, nothing can be done other than to wait a few hundred or thousand years for something to evolve to prey upon it and bring its numbers into balance with all the other kinds of plants currently drowning beneath this inedible green wave of supergrowth.
But there are many areas of Princeton where stiltgrass is just beginning to invade. Many yards still don't have it, or have small enough amounts to pull. Being an annual with weak roots, it is very easy to pull, and satisfying progress can be made if you have a small patch or many hands.
My strategy is to pick my spots, preferably pull it by late August, before it begins to flower, and just leave it on the ground to dry out. But even in September it can be pulled before the seeds begin to fall off. If it is already blooming and forming seeds, then either bag the pullings for the trash or, if you don't want to add to the landfill, pile it in one spot where any seedlings next year will be concentrated and easily dealt with.
We have made considerable progress in diminishing its presence at the Botanical Art Garden in Herrontown Woods, simply through persistent pulling to markedly reduce the production of seed.
A friend at the NC Botanical Garden has found that large patches of stiltgrass can be treated effectively, before seed production, with a very dilute (0.5 %) solution of herbicide. Annual plants don't invest much in roots, and stiltgrass's weak root structure makes it more susceptible to systemic herbicide than perennial plants that may be interspersed.
Virginia cutgrass (Leersia virginica), with its longer, narrower leaves and more spread-out seedhead.