I've published posts in 2014 and 2015 on my approach to dealing with stiltgrass, and I've had to go back several times to remind myself of what to do and when. So here goes...
|Freshly pulled Japanese stiltgrass. There is a lot of leafy growth |
for the relatively small root system.
|Letting the pulled stiltgrass sit in the sun for a day or two helps to kill it |
and it reduces the weight of the debris. Before pulling,
the stiltgrass in the bed was about 3 feet tall.
In areas to large for pulling I usually wait until blooming is just starting (end of August-early September) and then weed whack it close to the ground. The idea here is to prevent another season of seed from maturing. Unfortunately stiltgrass is very slow to decompose and can form a mat layer that also shades out the native seed bank. Where the cut grass is particularly thick I try to rake it together in piles in the shade where any viable seed is less likely to germinate.
For lawns that are full of stiltgrass the recommendation that I'm am trying to follow is to leave it unmown from late July to late August. Then, just as the flowers begin to form, cut the lawn at a lower level. The idea here is that constant mowing encourages the stiltgrass to form cleistogamus flowers low on the plant. These flowers self pollinate and are difficult to remove. While I'm not sure if it's true, it seems that letting the plant put its energy into upper open flowers will reduce the number of these lower flowers. These upper flowers can then be sheared off and the plants may not have time to recover with a second bloom.
The final stage for the lawn is to rake out the remaining stiltgrass in mid-September and overseed with a desirable cool season turf grass. The cool season grasses will germinate in the fall and fill the gaps previously inhabited by the stiltgrass.
|This shady area was solid stilt grass 4 years ago. Now, after 3 years of annual weed whacking |
and some pulling there is more diversity. The tall grass here is Virginia wild rye, Elymus virginicus,
which is now going into bloom