Plants That Repel Bugs and Pests

By Julie Christensen

There’s nothing that ruins summer fun faster than a swarm of mosquitoes, flies or hornets, yet most chemical solutions are hardly appealing. Mosquito repellents are sticky, oily and smelly, and the chemical compound DEET has been found to be toxic for children. Citronella candles work with limited effectiveness.

Fortunately, many plants are natural pest repellents. These plants usually have volatile oils or strong fragrances that deter pests. The plants can be used not only to scare mosquitoes off the patio, but to deter bugs in the garden, as well. Here, we’ve included a round-up of our favorite, hard-working plants for your pest-free garden.

Catnip (Nepeta cataria).

Cats usually love this, but mosquitoes don’t. Catnip, a member of the mint family, contains the essential oil, nepetalactone. A study conducted by the U.S. Department of Forestry Service found that nepetalactone is more effective at deterring mosquitoes than DEET. Best of all, catnip grows easily with almost no maintenance. Plant it in partial shade to full sun. Like all members of the mint family, it can become invasive in cool, moist conditions. Cut it back annually to keep it under control. If you have a cat who relishes it, protect it with bird netting or a basket.

Lime basil (Ocimum americanum).

This edible herb has a slight lime scent that deters mosquitoes and other insects. Grow it in moderately fertile, moist soil in full sun. Pinch back the leaves to encourage compact growth.

Rose-scented monarda

What if the pleasing scent of roses deterred pests? Rose-scented monarda is a perennial plant that produces the chemical compound, geraniol. This compound smells like roses, a pleasing scent to humans, but one that mosquitoes avoid.

Thyme (Thymus vulgaris).

You thought thyme was just for flavoring soup and roasted chicken, but turns out it’s an effective mosquito repellent. This perennial herb releases essential oils that are as effective or more effective as DEET, according to a study at Seoul National University in Seoul, South Korea. The oil lasts as long as DEET too.

Insect pests can quickly cause havoc in the vegetable garden, but some strategic planting can keep them at bay. Here are a few suggestions from Cornell University Cooperative Extension.

1. Aromatic herbs, including chives, garlic, peppermint, dill, coriander, fennel and mustard deter a variety of pests, from aphids to flea beetles. Plant these herbs throughout your garden. Remember, though, that members of the mint family are likely to get carried away. Consider growing them in pots placed in the garden.
2. Nasturtiums and icicle radishes deter squash bugs on cucurbits. Soak nasturtium seeds in water to soften their seedcoats. Plant them outdoors after the last expected frost. Radishes can be planted a few weeks before you plant the squash.
3. Fennel, garlic and rosemary are reported to deter slugs and snails.
4. Borage, calendula and thyme can stop the rampage of a tomato hornworm.
5. Japanese beetles love to eat 4 o’clocks, but the toxic leaves soon do them in. Remember that this plant is toxic to humans and other animals as well, so use care when planting it.
6. Petunias repel many insects, including aphids, leafhoppers, tomato worms and asparagus beetles. Imagine how pretty the vegetable garden would look with a few flowering petunias.

The image of long, straight rows of vegetables, such as those found in Mr. McGregor’s garden, has remained with us for many years, but it’s hardly the most efficient way to garden. A single crop grown in large amounts in one area is a bit like a neon buffet sign, beckoning the pests that feed on that crop. The garden that mixes up crops and intermingles them with aromatic herbs and flowers is much more confusing to insects, and much less enticing.

To make the most of pest-deterring plants, spread them throughout the garden. Since some insects overwinter beneath the soil, it’s a good idea to rotate crops so they don’t grow in the same spot twice. Floating row covers is another organic strategy that bars pests from ever making their way into your luscious garden.

For more information on organic pest control and pest-deterring insects, visit the following links:

Companion Planting from Cornell University Extension
Use Plants for Pest Control from the University of Illinois Extension

Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.