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Does cayenne pepper kill grass?

There are a variety of situations where you might consider applying cayenne pepper to your yard. Cayenne pepper is high in capsaicin, which is the chemical compound that makes chili peppers spicy. And after all, chili peppers developed this spice to deter it from being eaten — so many people apply cayenne to their yard hoping to deter hungry visitors.

But the question many people have is, “is cayenne safe for grass, or will it kill my lawn?”

Fortunately, cayenne pepper will not kill your grass or otherwise harm the quality of your lawn.

Plants don’t have the same nerve endings as humans and other animals, so the capsaicin in cayenne won’t harm most plants.

However, it’s possible that cayenne might otherwise disturb the ecosystem of your yard.

Does cayenne pepper harm earthworms?

Earthworms live in the soil below your lawn and help aerate it and increase permeability. There is little research into whether or not cayenne pepper, or the capsaicin found within cayenne, is harmful for earthworms. Some people hypothesize that worms have TRPA1-like channels, which is the nerve ending in humans that is irritated by capsaicin, sending pain signals to the brain. One study found that Canadian nightcrawlers could detect allyl isothiocyanate (the compound that makes mustard and wasabi spicy), but not Vanilloids, the family that capsaicin and Piperine (black pepper) are grouped under.

Stories around the web will caution you against composting hot peppers for fear of harming worms, but again, there is little direct scientific evidence exploring this topic.

How to apply cayenne pepper to your yard to deter critters

Cayenne pepper is used as a contact repellent for animals like deer, meaning that you apply it straight to a high-value crop so that when a deer tries to eat it, it is deterred by the spiciness. However, if you apply cayenne pepper to a plant that you want to eat, like fruits or vegetables, the spicy flavor can remain and ruin the food.

Other people suggest that cayenne pepper can repel insects like mites, aphids, thrips, and whiteflies, which may be things you are trying to keep off your lawn or out of your yard. As with any pesticide, it should be used with caution because each insect has a distinct function in your ecosystem, and eliminating any one insect can cause a chain reaction.

You can make natural homemade deer and pest repellents using three forms of cayenne: powder, hot sauce, or fresh peppers.

Cayenne powder

To make an insect or deer repellent out of cayenne powder, add two tablespoons of cayenne powder to 1 gallon of water and stir or shake vigorously. Allow it to sit overnight, and then carefully transfer it to a spray bottle.

Hot sauce

Using cayenne hot sauce rather than cayenne powder can be a good choice because it dissolves more easily and will not clog a spray nozzle. Use a ratio of 1:16 cayenne hot sauce to water, so for example you would use 1oz of hot sauce and 2 cups of water.

Fresh cayenne peppers

If you grow cayenne peppers in your yard, you can make a natural repellent using your own harvest! Add 1/2 cup of chopped peppers to 2 cups of water and allow it to sit overnight. Strain away the pepper pieces before transferring it to a spray bottle.

Use cayenne in your yard with caution

We are not always exactly sure how cayenne pepper will impact the critters in our ecosystem, but what we do know is that it is an irritant to humans. If you want to apply cayenne pepper to your lawn or vegetable garden, be sure to handle it with care. You may want to wear gloves and goggles and make sure that you are not breathing in cayenne powder or aerosolized cayenne.


  1. Eui, K. (2019). Eisenia hortensis Detects Chemesthetic Irritants through TRP Channels. Wake Forest University ProQuest Dissertations Publishing.
  2. Gegner, L. (2003, June). Deer Control Options. Food Safety. Retrieved September 20, 2022, from
  3. Silver, W. L., Kim, A. H., Kim, E. Y., & Saunders, C. J. (2019). A novel T-Maze Assay to evaluate chemical irritants on Lumbricus terrestris. Applied Soil Ecology, 133, 186–189.

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