Can your garden repel mosquitoes?

Lemon thyme, marigolds, lavender, scented geraniums, and a number of other plants are often touted as having mosquito-repelling properties. You might notice them in the garden center with tags claiming “natural mosquito repellent” or “keeps mosquitoes away,” or see them in lists on social media and other internet sites. Most of the plants advertised or listed as such do have some repellent properties, but simply planting them in your garden does not do the trick.

For a plant to be effective at repelling mosquitoes, its leaves, stems and/or flowers must be crushed to release the fragrance from the plant. Then, the oil or sap from the plant must be applied to skin or clothing in the same manner that a commercial mosquito-repellent spray would be applied. Think of it this way — would spraying a can of mosquito repellent into the air in your yard keep the insects away? Or just setting the can on patio table? Either of those options are largely ineffective, just like simply setting a supposed mosquito-repellent plant in the garden or crushing its leaves periodically.

If you think you want to try growing mosquito-repelling plant species and applying it to your skin, try it on a small patch of sensitive skin a few times before rubbing it all over. Skin irritation or allergies can occur with any species. Also, you will want to make sure it is a scent with which you are comfortable for a few hours. For example, marigolds may be less personally and socially acceptable than basil or lemon balm.

What plants are best? Lemon thyme is generally considered one of the most effective, and it has a pleasing scent. Others plants commonly recommended for mosquito repellents are basil, rosemary, garlic, lemon balm, sage, scented geraniums, catnip, catmint, citronella plant and citronella grass.

Studies regarding the effectiveness of these plants are few and results sometimes contradictory. But anecdotally, some gardeners swear by them. They are certainly worth a try if you are interested in a natural repellent and enjoy smelling like your plants.

The culinary herbs listed are pleasant options, especially if you are already growing them. Garlic might be used with caution as it will keep more than mosquitoes away. Catnip and catmint are two completely different plants and listed in a range of references with seeming confusion between the two. Catnip should also be used with caution, especially for cat owners.

According to the EPA website, the following plant derivatives are listed as active ingredients in skin-applied insect repellents: catnip/catmint oil, oil of lemon eucalyptus, and oil of citronella. The EPA has also designated several active ingredients as minimal risk and therefore exempt from registration, including citronella, cedar, geranium, peppermint and soybean oil. EPA tests for safety but not efficacy.

If mosquitoes are especially bad around your home, the best way to reduce the number of them is to eliminate standing water. Improve drainage in low spots, holes, etc., or install plants that tolerate wet soil to help soak the water up more quickly. Make sure gutters drain properly. Change the water in birdbaths, use a pump to circulate water in landscape ponds, and get rid of buckets, unused flower pots, old tires, and anything else around your yard that holds water after a rain event.

Adult mosquitoes hide in vegetation, so keeping lawns mowed and weeds at bay can also help deter the insect.