Does Tenacity Kill Crabgrass (How to use Tenacity to Kill Crabgrass)

Tenacity is one of the most popular herbicides on the market. It has an edge over Roundup by being a selective herbicide. Tenacity will kill weeds, but not your lawn. But what if you have pesky wild grasses like crabgrass? Does Tenacity eliminate those? Find out in this article!

Does Tenacity Kill Crabgrass?

The short answer is “yes, Tenacity can kill crabgrass.” Some lawn owners swear by it to eliminate crabgrass. But how do you use it, and what makes it so effective against a weed so tenacious it tests the limits of Tenacity’s name?

How Do You Use Tenacity to Kill Crabgrass?

First, follow the instructions on the bottle to mix Tenacity properly. Failure to do so may dampen Tenacity’s effectiveness or bleach your lawn. Use any personal protective equipment necessary to keep this process as safe as possible.

It is best to use your Tenacity within 24 hours of mixing. You may also wish to check the weather; do not use Tenacity shortly before it rains.

As a general rule, you should apply Tenacity to your lawn in Spring before any weeds pop up. Although Tenacity is good for both pre-and post-emergence, you want to focus on early spraying for crabgrass in particular. It struggles with mature crabgrass, but that is for another section.

To keep track of where you have and haven’t sprayed, it may help to put some turf color into your mixture. Add 1 teaspoon to your Tenacity mixture for the best results. This will not alter its potency at all. Don’t stop until you have sprayed Tenacity all over your lawn.

Note that, even though Tenacity is safe for pets and children after it dries, it is still a poison. Treat it like you would any toxic chemical. Follow all the instructions while mixing. Allow it to sit for at least two hours before letting children and pets on your lawn.

How Long Does It Take Tenacity to Kill Crabgrass?

Regardless of what weed(s) is in question, you should reapply Tenacity every 2–3 weeks. It will not kill crabgrass any faster than that. The main ingredient in Tenacity, mesotrione, is a slow killer by nature.

Mesotrione interferes with a plant’s ability to photosynthesize. It also blocks growth hormones within the plant. As a final barrier, this chemical also gets into the soil. This combination makes it an amazing pre-emergent weed killer. The grass on your lawn uses different methods of getting nutrients, so it is not affected by Tenacity.

In theory, Tenacity kills crabgrass before it has a chance to get started. It is best applied when the plant is still growing. But what should you do if you see a new crop of crabgrass appear on your lawn, despite your best efforts?

Will Tenacity Kill Mature Crabgrass?

If you want to use Tenacity to kill mature crabgrass, you can. Spray Tenacity on the spot and the crabgrass will be dead within 2–3 weeks. Reapply after that period.

Tenacity can kill mature crabgrass, but people have been shamed for not applying it in the Spring. If you want to use Tenacity to kill crabgrass late in the season, it is valid. However, it will look white for 2 to 3 weeks before dying. It works, but not as fast as some people would like.

Some sites will tell you that Tenacity either does not work late in the crabgrass season or that there are better options. The two that come up most frequently are quinclorac and sethoxydim. Both of these are post-emergent weed killers that work well on mature crabgrass. They are available under various brand names, so look for these chemicals online before heading out to buy some. Both of them will work wonders on mature patches of crabgrass.

In short, Tenacity works on mature crabgrass, but it might not be the best option. It’s slow, possibly too slow to be effective, and the other two chemicals mentioned are faster for post-emergent treatment. Remember to apply Tenacity in the Spring of next year!

Will Too Much Tenacity Kill My Grass?

If you use Tenacity as directed, your lawn will be safe. However, mixing Tenacity incorrectly or applying too much may damage your lawn. Tenacity may bleach good grass around your weeds. Please follow all instructions carefully when using Tenacity.

What Other Weeds Does Tenacity Kill?

Tenacity kills many stubborn weeds, including, but not limited to:

  • Crabgrass
  • Bentgrass
  • Dandelions
  • Ground ivy
  • Nutsedge
  • …and more!

Regardless of what weed you want to kill, Tenacity is best applied in Spring. It also requires another application after 2–3 weeks. Your weeds will not die immediately.

Please consult your local garden center if you have questions about a particular plant. Some of your questions may be answered by reading labels, but it never hurts to have outside input if you need a different herbicide.

I Have Multiple Types of Grass on My Lawn. Will Tenacity Hurt Them?

Tenacity is safe for most common types of grass used for lawns. However, another herbicide, sethoxydim, works particularly well on lawns that have centipede grass and crabgrass. If you have questions, please consult your local garden center about sethoxydim and its interactions with different plants.

Should I Mix Tenacity with Other Herbicides?

You may have seen some advice about mixing Tenacity with other weed killers. It is ill-advised to mix toxic chemicals of any kind, herbicides included, because you do not know how those chemicals will react with each other. If you must try homebrew cocktails, do so in a well-ventilated area and use the proper protective equipment.


Tenacity is a versatile, relatively safe herbicide that kills weeds, but not your lawn. The list of weeds that it works on includes crabgrass…with a few catches. The first major catch is that Tenacity requires multiple applications and takes a while to work. The second catch is that it is significantly less effective on mature crabgrass. If you want to get rid of mature crabgrass quickly, you are better off using another chemical.

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