I’ve been curious to learn more about companion plants lately, and I wanted to dive in a bit deeper into those which help prevent pests and diseases. So, I did some research. Here’s what I found.
To repel pests in your garden, plant companions such as nasturtium, dill, lavender, and rosemary. Nasturtium planted next to vegetables protects them from squash bugs, bean beetle, aphids, and white flies. Interplant lavender, sage, and rosemary to prevent ticks, snails, slugs, deer, and other browsing animals.
Let’s take a look at some of the best plants that repel pests, and what to plant them with.
Plant nasturtium next to squash and other vegetables. By doing this, you can prevent pests from your vegetables like squash bugs, bean beetle, aphids, and white flies.
Nasturtium is occasionally thought to be a weed, but it’s gaining popularity as one of the best companion plants around. It’s great at attracting pollinators such as hummingbirds due to its super sweet nectar and longer flowers, but it’s also useful to repel pests.
Well, repelling might not be the right word, as its sweeter nectar actually attracts aphids away from other plants (source).
Aphids love fruit trees, sweeter herbs, and most other garden plants, so using nasturtium to attract them away from your other plants can save you a lot of trouble from having to deal with them yourself.
Nasturtium itself can handle aphids and often won’t get overrun by them. However, if you find your garden is getting overrun, consider planting dill, calendula, and cosmos.
2. Calendula and Cosmos
Calendula and cosmos are both flowering plants that attract beneficial wasps and hoverflies. I know, I know—how can ANY wasps or flies be beneficial? Who would invite these “pests” into their garden?
However, some wasps, such as paper wasps, feed on caterpillars, which we know are all too often damaging to plants. They take the caterpillars back to their nest, where they feed them to their larvae (source).
But, like most balanced ecosystems, the wasps don’t consume all of the caterpillars, leaving just enough of them to prevent major plant damage and develop into butterflies—pollinating the garden.
So, it’s effectively a win-win. You avoid decimating caterpillars, your garden gets butterflies, and the wasps get a snack. Oh, and you get some pretty nice flowers too.
Hoverflies are also beneficial as they prey on aphids, reducing their population to reasonable numbers as well. As a bonus, planting nasturtium with your calendula and cosmos will keep aphids manageable. Additionally, many flies, including hoverflies, assist in pollination, although not as well as bees (source).
The tansy flower is another flower used to repel ants.
Small note: calendula is also called a pot marigold, but it’s not the same as a traditional marigold. However, they are in the same family.
To see more companion flowers, check out my other post: The Top 10 Companion Flowers for Gardens, Vegetables, & More.
Planting dill next to corn can prevent corn earworms.
Dill is another plant that prevents aphids. Only this time, it’s done by attracting ladybugs—a common aphid predator.
Ladybugs also eat spider mites, which, like aphids, suck the sap from plant tissues. This leads to issues such as yellow or brown spots on leaves. Aphids and the like are commonly found underneath the plant’s leaves.
By planting companion plants that attract ladybugs, such as dill, and releasing them into your garden, you’ll have one more method of aphid and pest control.
If you’re interested in releasing ladybugs in your garden, you can find ladybugs for sale at most nurseries.
4. Lavender, Sage, and Rosemary
For best results, interplant lavender, sage, and rosemary in your gardens.
These flowering herbs repel pests while significantly increasing pollination. For example, the purple sage in my parent’s backyard is always attracting bees, butterflies, and other pollinators.
Their potent scents repel many pests including ticks, snails, slugs, deer, and other browsing animals (source).
While lavender, sage, and rosemary attract pollinators and some beneficial insect predators, their main method of pest control is their strong scent.
Lavender is an active ingredient in many bug sprays, and the plant is found to have similar effects. For example, here in Austin, Texas, we used lavender spray to deter scorpions from entering our home.
5. Garlic, Chives, and Onions
Garlic is a great at repelling Japanese beetles.
Garlic, chives, and onions are all part of the same family and, no surprise—they’re more potent-smelling than the above aromatic plants. You can plant these next to raspberries and strawberries to protect them from pests.
You can interplant any of these onion-family plants with just about any other plant, except for legumes.
The pest-repelling aspect of these plants likely comes from their ability to accumulate sulfur.
You can also combine garlic, chives, or onions with some or all of the other pest-repelling plants on this list to make an aphid knockout team.
Mint is a great companion plant for your garden when it comes to repelling certain pests. Mint is shown to prevent fleas, ticks, cabbage moths, beetles, and even mice.
Grow mint near marigolds (which is also a great repellant), cabbage, oregano, carrots, kale, tomatoes, cauliflower, peas, and beans.
Like lavender, mint is an active ingredient in many bug sprays, and the plant is found to have similar effects.
Due to basil’s strong aroma, this herb is known to repel flies and mosquitos.
Plant basil near marigolds, oregano, and chives. All three of these companion plants deter many different pests, so they are great options to plant each other with.
Four volatile compounds in basil plants interrupt the mosquito’s heat and carbon dioxide sensors, reducing their ability to recognize a meal (source).
How Companion Plants Prevent Pests
If I could use one word to explain most of our experiences with pests, it would be defeating.
However, this is mainly because we’ve been overly dependent on monocropping. For example, if only one cabbage gets infected with a pest or disease, nothing is stopping that pest or disease from spreading swiftly to the other, adjacent cabbages.
On the other hand, by intercropping, the natural diversity of plants limits and sometimes completely prevents many pests. This is due to intercropping serving as a natural genetic wall or barrier, either containing the infection to a single plant or bringing certain traits which repel it completely.
Plants that repel pests usually do so by emitting a natural substance either through their roots, flowers, or leaves. As a result, many of these plants make popular and useful companion plants.