|Here in mid-October you can see the height difference |
between the regular flowers and cleistogamous ones.
An approach that I am expanding on further this year is to use a stiff rake to pull out the stilt grass from the lawn. This works best when the desired grass is clump forming. The rake can get locked into the creeping stolons of the stiltgrass, while the clumping grasses are not snagged (too much). Timing is critical -- wait until late in the season when the expanding lateral growth of the stiltgrass makes it easier to snag, but before the cleistogamous seeds begin to mature. This year I did a thorough raking at the end of September. That worked out with the timing for overseeding the lawn with a more desirable grass seed. When I went out a week later I noticed that some of the stiltgrass in the lawn did have seeds forming in the lower stems. Next year I will do the raking in early or mid-September to reduce the chance of actually spreading any matured stiltgrass seed while raking.