"Grass" Invading my Woods

Asked June 27, 2019, 5:35 PM EDT

This stuff has settled in almost overnight. Can you identify it, and also tell me how to KILL it? I appreciate this service!

Montgomery County Maryland invasive stiltgrass plant care weed

6 Responses

This is a highly aggressive foreign invasive plant known as Japanese stiltgrass. It is extremely destructive to parks and natural areas (woods) because it loves shade and spreads at lightning speed.

If you have not seen it before and are seeing it in scattered pockets, you are very fortunate. You should be able to halt spread if you are vigilant.

It is an annual. All these plants came up from seed from stiltgrass you didn't notice last year.

It has almost no root. Hand-pull small patches like the one on the left.
For larger patches such as in the right photo, you can hand-pull or use a string trimmer to clear it down to bare earth, leaving no root.

Do not let it survive to produce seeds in late August-early September. Seeds can stay alive in the soil for 7 years.

Here is our page about stiltgrass--read it carefully. It's good you are catching this early! https://extension.umd.edu/hgic/topics/japanese-stiltgrass

You might want to warn neighbors if they are not familiar with this invasive plant and it is new in your neighborhood.

Ellen

This is a highly aggressive foreign invasive plant known as Japanese stiltgrass. It is extremely destructive to parks and natural areas (woods) because it loves shade and spreads at lightning speed.

If you have not seen it before and are seeing it in scattered pockets, you are very fortunate. You should be able to halt spread if you are vigilant.

It is an annual. All these plants came up from seed from stiltgrass you didn't notice last year.

It has almost no root. Hand-pull small patches like the one on the left.
For larger patches such as in the right photo, you can hand-pull or use a string trimmer to clear it down to bare earth, leaving no root.

Do not let it survive to produce seeds in late August-early September. Seeds can stay alive in the soil for 7 years.

Here is our page about stiltgrass--read it carefully. It's good you are catching this early! https://extension.umd.edu/hgic/topics/japanese-stiltgrass

You might want to warn neighbors if they are not familiar with this invasive plant and it is new in your neighborhood.

Ellen

Yes, thank you for that.
So, maybe a deduction: At any time before late Aug/Sep, if you cut it with weed wacker or lawn mower, disabling the opportunity to produce seeds, then it should not proliferate. (?).
I've cut it with a mower, then sprayed with RoundUp. That should also do it, right?
Finally, if it grows "somewhere", and produces seeds, it will NEVER be discouraged; then, there is no forest floor... it's all lawn!
Right?
Thanks!
ed

Mowing does not kill this plant because it leaves the roots. The remaining plant sends out new shoots, that will produce seeds, the surviving shoots are just lower.

RoundUp is very effective on large patches, but glyphosate (the important ingredient) can be harmful to soil. Use as sparingly as possible.

Since you have some plants, it's likely there are a few seeds left in the soil that have not sprouted yet. So, you'll have to be on the lookout.

It's a good idea to stroll through to patrol your woods a few times during the growing season to pull the occasional stray stiltgrass plant. Yes, if you do not it will become a solid mass of stiltgrass. No forest floor.

Ellen

Thanks, Ellen! What I've been doing is mowing, THEN spraying with RoundUP. That should kill the roots, don't you agree? Also, on the stiltgrass that's maybe 15" tall, I simply sprayed the "leaves", and that sure does look like it works, all the way down to the roots. Please let me know if I've missed something!

When using an herbicide like Roundup that contains glyphosate do not mow first. The active ingredient enters the plant through its foliage and then travels down to the root system.

Deb