Weed killers that are all-purpose killers are able to kill crabgrass, but they will also kill your lawn. Use these non-selective killers only in places where you can avoid spraying them on desirable plants.
Natural or organic products may be available in your area. These are often derived from plant oils, sometimes they are salt-based products. Even vinegar, at full strength, can kill crabgrass and other weeds. Typically these will be non-selective, and will also cause damage to your lawn. (Vinegar at a normal household concentration of 5% is not strong enough to kill crabgrass with one application.)
Another natural method to kill crabgrass is to pour boiling water on the weed. This usually kills any weed. It also usually kills everything. A creeping grass like Bermuda or St. Augustine may recover from such a treatment, but test it on a small area first if you are inclined to try it.
A Last Resort?
When crabgrass has grown to the point of forming a dense mat or clump, it may have smothered your good lawn grass. If this is the case, you will have to reseed the area. In this situation, it may be acceptable to use a non-selective weed killer, since the crabgrass is a worse problem than losing a bit more grass.
The Slow Way To Kill Crabgrass In Lawns
Put on a pair of gloves. Grab a serrated knife or a V-shaped weeding tool. Slice into the root of the crabgrass. Pull up the weed and discard. Repeat.
No fun? But all kidding aside, sometimes that is not a bad approach. You might be surprised what you can accomplish by taking 15 or 20 minutes each evening. Start on one side and methodically work your way across the yard. You can cover a good size area each week this way.
Winning The Crabgrass War
The key factors in being able to successfully kill crabgrass are worth summarizing:
- Start early. Killing young plants is easier with less potential harm to lawns and desirable plants.
- Kill crabgrass before it goes to seed to avoid next year’s war.
- Stay alert. New crabgrass plants can start throughout the warm growing season.
- Follow label directions accurately to prevent bad results. Be persistent and be patient. Try to kill crabgrass at least partially during the warm season, and then prevent its return.
- Know your enemy. Read up on Crabgrass. It will die off over winter and sprout from seed in late spring. The more you know the better you can prevent the spread.
- This article has focused on how to kill crabgrass that is already growing. Crabgrass prevention is an important strategy for long term effectiveness. Consider using a pre-emergent for prevention.