If you recall, I wrote one of my first blogs was about the invasion of Japanese Stiltgrass in our area. It is, in fact, choking out more and more of our native plants than expected. I took one of my pictures behind someone's house where the stilt grass has taken over. We may be getting frustrated with it in our own lawns, but it is also becoming more of a problem than it looked this spring.
As a reminder, this annual grass goes through its entire lifespan in one year's time. It is now reaching the end of it's life but it has spread its seeds getting ready to start growing next year. Soon, the existing plants will die back and leave a nice brown patch in your lawn as well as on the perimeter of the woods and deeper into our natural spaces. You can see it all over Reston's paths.
Springtime is a the best time to control this very adept annual grass. This past year, I personally used Preen which is a pre-emergent annual weed control for crabgrass and numerous other weeds. It needs to be spread BEFORE the weed germinates for its year of terror! The best point of reference is to apply it when the Forsythia is blooming. Since Preen has an effective life of 3 months, you will need to REAPPLY in the June timeframe. Both my neighbor and I realized that the Japanese Stilt Grass has a second germination period because it appeared in both of our yards in the June/July time period.
Also, since Japanese Stiltgrass is an ANNUAL grass, you can safely apply Preen to your flower beds where you have perennials planted. As I mentioned back in the spring, the major active ingredient for Preen is Corn Gluten. This ingredient is very popular in annual weed control. If you do not want an "inorganic" product like Preen, there are "organic" versions available"WOW! Supreme a Pre-emergent Weed Control and Control and Fertilizer" that is heavy on corn gluten for weed control.
Since it is now the Fall, you need to plan ahead but act NOW! It is time to fertilize your lawn and reseed. This needs to be done BY October 15 to be most effective. Even though you may think Spring is the time to do this lawn work, when planted in the Fall, the roots of the new grass seeds can become established before the onset of winter. Then, when the warmth of Spring comes up on us, the grass should not die off and it will hold on to the rains a bit more.
Time to tackle your personal lawn crises by seeding now. Water. Put down a pre-emergent weed control in the Spring and again in early Summer. Keep watering. Your lawn should be nice and free of Japanese Stiltgrass next year! Fingers crossed for you (and ME!) as we tackle the maintenance of this aggressive weed.
Laurie Dodd
8:01 pm on Monday, October 8, 2012
Molly, I am one of many who has found my lawn taken over by japanese stilt grass. I have pulled it by hand from one large area of my lawn and re-seeded, but the rest will have to be treated with a pre-emergent weed killer in the spring. I wonder whether overseeding this fall will work on the vast expanse of lawn that is now covered with stilt grass - will the grass seed be able to grow with this invader already in place? I will give it a try, but I may have to seed again in the spring.
Laurie Dodd
8:09 pm on Monday, October 8, 2012
While the small plants shown in your first photo have not yet gone to seed, it is best to keep this stuff mowed down low. The tall grass in your second photo is producing numerous seeds that may be in the soil for many seasons to come.
Molly O'Boyle
1:09 pm on Wednesday, October 10, 2012
Exactly right, Laurie. The tall grass, which is in its seed stage of life, has produced seeds that are being spread by numerous means all over the neighborhood. I believe that overseeding will indeed help/work this fall because, once mowed down, the existing grass will be nearly dead at this point. Since it will not be soaking up any excess moisture from the soil, the new grass seed can use it to grow and get established.
The Merrifield Garden Center Facebook page noted this past week that it is time for a second round of fertilizer at this point. I will take care of that after the leaves get picked up from my yard!!