CO-Horts: Annual Weeds

Posted by Kara Harders, Regional Small Acreage Management Specialist, Peaks and Plains Region

Cheat grass, gone to seed

Getting rid of weeds sounds like a simple idea but most of us know it is easier said than done. This post talks about controlling annual weeds, not perennials. Always try to identify the weeds you are dealing with so you can plan the most effective attack plan.

As I take my socially distanced walks around the neighborhood I am always disheartened at the sheer volume of annual weeds I see taking over peoples yards, gardens, rocked areas, and flower beds. It isn’t that I think my neighbors don’t care, I think many of them do, it is just such a hard problem to cure.

The annual weeds are some of the worst because they come up in the spring when we are all dying to see green. They give us hope that the dead patch in the back alley or next to the driveway is finally filling in with the grass we want, and just a few months later we are irritated by the nasty seed heads stuck in our socks and pet’s fur or the dead brown patch they become.

Often times killing the annual weeds (be it Blue Mustard, Yellow Mustard, Cheat grass, Green Foxtail, Henbit, Kochia, Russian Thistle, or others) won’t do anything in the overall control of the weeds. Annuals are the quick and dirty plants of the world because they go to seed so quickly, often before we really have the chance to find and identify them all.

Foxtail, gone to seed

Instead of having it in your mind to kill annual weeds, have it in your mind to keep them from spreading seed. Since an annual weed only lives for a year and then dies, it’s entire specie depends on producing enough seeds to repopulate next year. This can be achieved (or at least attempted) in several ways.

Weed Early: If you can pull or otherwise root up the weeds when they are very small (less than 3 inches, and no sign of seed heads) they will likely die without reproducing (win!). If you don’t mind the look of little weed bodies all over, you can even leave them on the ground. No bagging for you! Herbicides are also an effective choice at this point (always read the label on herbicides! The Label is the Law).

Weed Often: Sometimes with cold and warm weeks and spring rains we will have “flushes” of new weeds coming up. So take a walk around your yard or property fairly frequently, it’s good for your health and also lets you keep on top of what is sprouting up.

You say you see weeds with seeds? It is easy to fall behind on weed watching. I know it happened to me this year. If you start seeing taller weeds or weeds with seed heads you know you have missed the easy window. I really am sorry for you because things get a little more labor intensive now.

Herbicides: If you were all for using herbicides, that window has closed, put down the sprayer. If you kill a happy green weed with seeds you will have the satisfaction of seeing it get sad and brown and die, but the seeds will survive your chemical assault and next year you will be back where you started.

Don't leave a pile of weeds with seeds!

Pulling: Pulling is a solid option. Annual weeds are usually easy to pull up and can be bagged and thrown away. Since the seeds exist try not to shake the pulled plants too much. You have to bag and throw them away at this point.

Mowing with a bag: If you just can’t possibly pull all the weeds consider using a lawn mower with a bag to collect your cuttings (and throw the mowed contents away). This method is sloppier than hand pulling and bagging but will collect more weed seeds than doing nothing. This works from some weeds but less on others, Kochia for example will just grow lower to the ground and form a mat of seed producing weeds.

Keep Weeding: You will likely need to do some level of weed control every year. Seeds from deeper underground will start to grow, wind will bring seeds from your neighbors, a rogue Kochia tumble weed will make its home in a corner of your fence and rain seeds on the ground, the possibilities are endless. But keep your head up, after the first year or two of keeping the seeds at bay you will probably see a good reduction in the weeds that come up, and after that hopefully you can work proper weed management into your schedule.

For more information and links to fact sheets visit: https://planttalk.colostate.edu/topics/weeds-cultural-problems/2117-landscape-weeds-control/