Monday, October 17, 2016

Last Comments on Stiltgrass -- This Year

I've been talking a lot about Japanese stiltgrass control and how I am trying to eliminate it from my property.  One of the really insidious features of stiltgrass is that in addition to its normal seeds produced on tall stalks, it also produces a second set of seeds on flowers enclosed in stems close to the ground.  These are referred to as cleistogamous flowers.

Here in mid-October you can see the height difference
between the regular flowers and cleistogamous ones.
While removal of the upper flowering parts of the plant will help control the spread of stiltgrass and reduce the total number of seeds produced, that second set of seeds keeps the local population going.  These cleistogamous flowers are particularly relevant in mown lawns, where these ground-hugging flowers survive the regular trimming.

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.

Here are the piles of stiltgrass and other debris I raked out in preparation for overseeding
the last week of September.  The 4 smaller piles are from an area I overseeded
with tall fescue last year; the larger piles are from a new area I started this year.
After drying for a couple of days these piles were carefully carried away to a segregated brush pile
to avoid spreading stiltgrass seeds.

A general strategy for removing invasive plants is to start with a manageable sized area and clean it up thoroughly.  In subsequent seasons expand the area for cleaning.  This reduces the chance that the previously cleaned areas become reinfested.  Trying to do too much at once risks leaving many seeds or plants behind that will reinfect your 'clean' areas and real progress will difficult.