Grow This Flower To Keep Pests Away From Your Carrots

Carrots are a relatively easy-to-grow garden staple, and there is nothing like the anticipation of tugging the frilly top of these root veggies to reveal the mystery underneath — hopefully a robust orange root ready for snacking. Sadly, your surprise might be a shriveled specimen that has fallen victim to one of the many carrot-munching pests that love them as much as you do. If this has been your experience in the past, it might be time to consider adding a companion plant that will better your chances of a healthy carrot harvest: tansy.

A fern-like plant topped with clusters of bright yellow button-like flowers, the common tansy (Tanacetum vulgare) has developed quite a reputation for its multiple benefits. This herbaceous weed (yes, it is considered a weed) was cultivated by ancient Greeks as medicine against everything from constipation to rheumatism. It is also associated with continued use in the early United States for treating fevers and intestinal issues, keeping vermin away from corpses, and even as a meat preservative. Some studies have shown that tansy oil might even help repel mosquitoes and even ticks. In the garden, tansy is known for its ability to deter pests like the potato beetle, and has been studied for its toxicity to larvae of moths and caterpillars. 

Like other weeds that you shouldn't pull from your garden, tansy is a hard-working companion plant. Beyond its repellent qualities, its bright yellow flowers also help attract beneficial insects like ladybugs and parasitic wasps, both of which will happily prey on the aphids, flea beetles, and flies that love your carrots. 

Common tansy prefers full sun but can do fine with some shade. Additionally, it can thrive in a variety of soil types, and will have no problem setting up shop in the sandy loam soil preferred by your carrots.  That said, its easy-going nature is actually a problem in some areas. 

Tansy comes from Europe and, although it is widespread in the United States and Canada, it is not native to North America. In fact, tansy is considered a noxious weed in many western states. Its repellant qualities are due to toxic components including camphor and thujone, which can be irritating to human skin and are toxic to livestock. This means care needs to be taken with how and where it is planted. Common tansy is actually banned in Colorado, Minnesota, Montana, Wyoming, and certain areas of Washington state. If permitted in your area, you can take additional steps to control the spread of tansy by deadheading spent flowers to control self-seeding.

Alternatively, if you live in a place where tansy isn't allowed, you can consider other companion plants to benefit your carrots that will help keep pests away. According to the Old Farmer's Almanac, other great companions include chives, rosemary, sage, and leeks.