Marigolds Vs. Wasps: Old Wives' Tale Or Effective Deterrent?

Marigolds are like bouncers in a garden, repelling unsavory pests with sensory confusion. For beneficial bees and other pollinators, though, they extend a friendly hand, inviting the nectar-carrying buggies to hang out near plants like cucumbers, tomatoes, potatoes, and carrots. Although this bit of wisdom might have been passed down through the centuries as an old wives' tale, there really is something to it, despite limited scientific research. 

For nasties, like wasps, marigolds can be a major yuck. We can blame this on how powerful the wasp's snout is. With its strong sense of smell, a wasp can find food easily, which is why those buzzing yellow-and-black menaces are so attracted to the steaks and Popsicles at your picnic. With a nose that finds all the goodies and a big stinger that hurts like a hot iron when it pierces your skin, the wasp is fairly confident it'll get what it wants come lunchtime — until something messes with the insect's olfactory mechanism to keep it away from your backyard barbecue, like a big planter box of scented marigolds.

This is why, if you're planting marigolds as companion plants for your fruits and veggies, planting them as a border around your food plants and sprinkling these orange flowers around your garden will help deter pests. That's the story according to folk wisdom, anyway. If you additionally have a problem with wasps flying into your home the moment you open a window, it can be helpful to plant some marigolds in a planter box below your window, too. 

Although any marigold can be used to keep wasps away from your home, some varieties are more pungent than others. The French marigold (Tagetes patula) boasts the strongest anti-bug smell. If you can only pick one kind of marigold for your anti-wasp campaign, this is a good bet to grow as an annual in your garden.

Another lesser-known marigold species is called signet marigolds (Tagetes tenuifolia). They're worth a mention because they give off the scent of citrus when they're crushed, and wasps shy away from the smell of citrus for the same reason as they do marigolds. (This seems to be as much an old wives' tale as it is science.) As such, other plants with citrus scents, like lemongrass, have been used as spatial repellents against wasps. As for their growing zones, signet marigolds are grown as annuals in zones 2 to 11. 

If you'd like some added protection, include some other plants that wasps hate, such as peppermint and lemongrass, in your plantings. In the latter case, you're giving the wasps a double dose of a bug-deterring chemical called "geraniol," which, although it's commonly associated with geraniums, is also found in some marigolds, specifically, African marigolds (Tagetes erecta), and lemongrass. Any combination of those plants has the potential to throw off the wasps' internal compass and away from you and your picnic.