For daily wit & wisdom, sign up for the Almanac newsletter.
As spring and summer flourish, so do the biting bugs! Can plants alone really repel mosquitoes and other nuisance insects in the garden? Here’s what the science says, as well as a list of plants with actual insect-repelling properties.
Mosquitoes are more than a nuisance, as there are many mosquito-borne diseases out there, including viruses such as West Nile, Eastern Equine Encephalitis, and Dengue. It’s not just mosquitoes, either—gnats, biting flies, ants, and other pests can take the fun right out of any outdoor activity.
Do Mosquito-Repellent Plants Really Work?
Mosquitoes and many other biting insects target their victims by the odors and gases we give off—carbon dioxide, sweat, and smelly feet to name a few. Mosquitoes, for example, can be attracted by the carbon dioxide in our breath from as far as 150 feet away.
Luckily, the strong scents produced by some common garden plants can block the scent receptors that the bugs use to find us—but simply including strongly scented plants in your garden isn’t enough to keep the bugs at bay. In most cases, a much stronger, more concentrated amount of a plant’s scent is needed to throw the bugs off your trail.
It’s All in the Oils
The key to generating a strong enough insect-repellent scent is to release the essential oils within a plant’s leaves. These oils are what actually have the insect-repelling effect. Burning sprigs of the plant or crushing the foliage are the best ways to release their oils.
At home, it’s easiest to crush the leaves and apply them topically whenever you’re working in the garden. Simply pinch off a few leaves and crush them in your hands to release their essential oils, then rub the crushed leaves on your skin to create a mosquito-repellent layer.
(WARNING: Be wary of allergies! Direct contact with the oils of some plants may irritate the skin. We recommend testing the crushed leaves on a small part of the underside of an arm or leg before applying it elsewhere.)
It’s important to keep in mind that although some plants may indeed repel insects, using them as suggested below will not produce the same insect-repelling results as commercial insect repellents, which have been engineered for effectiveness and longevity. In most cases, using the leaves from a plant will only provide moderate protection for a short period of time. As a rule of thumb, if you can’t smell the scent on yourself any longer, it’s probably not keeping the bugs away anymore!
Which Plants Have Insect-Repelling Properties?
Many plants that are labelled as “insect-repelling” are, in fact, not. Specifically, the so-called “mosquito plant,” Pelargonium citrosum, has shown little to no evidence of repelling mosquitoes, despite its name and pleasantly lemon-scented leaves.
So, here are a few scented plants that actually have insect-repelling qualities when used correctly:
Lemon grass(Cymbopogon citratus) and citronella grass(C. nardus) have proven mosquito-repelling abilities thanks to the citronella oil contained within their leaves. The leaves can be crushed and rubbed on bare skin to ward off biting bugs. Tall, tropical grasses, lemon grass and citronella grass will only survive as perennials in frost-free zones; those who live in colder climates will need to keep them in pots and bring them inside when temperatures drop in the fall.
Lemon thyme(Thymus citriodorus) is another citrus-scented plant that can be used as a topical insect repellent. Burning sprigs of lemon thyme (on the outdoor grill, for example) is also effective at keeping nuisance insects away from the immediate area.
Lemon balm(Melissa officinalis), like lemon thyme, gives off a scent that’s offensive to insects. Apply it topically. If you’re planning to grow it, keep in mind that lemon balm is in the mint family, so confine it to a pot to keep it from spreading like crazy!
Lavenderhas a strong scent that canrepel moths, flies, fleas, and mosquitoes. Use it fresh or dry some of the flowers to hang around the house or put in with your clothing to keep bugs out. Here’s how to make lavendar sachets.
Garlic keeps away more than vampires. To be effective against bugs, however, the cloves must be rubbed on the skin, which may end up being more offensive to other humans than to insects. (Sadly, consuming garlic hasn’t been shown to keep the bugs away.)
Rosemary may prevent flies and mosquitoes from ruining a cookout. If the bugs are really bad, throw a few sprigs of rosemary on the grill and the aromatic smoke will help drive the mosquitoes away.
Basil(Ocimum basilicum)is a culinary herb that does double duty by repelling flies and mosquitoes, too. It’s one of the most pungent herbs and even gives off a strong scent without its leaves being crushed. If you’re looking for an insect-repelling plant that you can “set and forget,” basil is your best bet.
Catnip(Nepeta cataria) contains a substance called nepetalactone, which has been found to be even more effective than DEET at repelling mosquitoes in lab trials. Unfortunately, when crushed leaves were applied topically, catnip appeared to have little to no insect-repelling effect, so don’t depend on this plant to keep the mosquitoes away.
We’re sure there are other plants that have acquired a bug-repelling reputation, but we wouldn’t depend on only a few plants to make our yards insect-free. One of the most effective things you can do to cut the mosquito population down is to eliminate any standing water where their larvae may be living.