The Biology Behind Plants To Drive Away Pests


The Biology Behind Plants That Drive Away Common Pests guest written by Richard Gillespie

Looking for some eco-friendly ways to get rid of pests in your garden? Why not give pest-repellent plants a try? Certain plants have finely tuned defenses to protect themselves from attack. By understanding the biology behind these defensive strategies, you can put them to work for you.

Scents That Make Sense

Many plants use chemical compounds to drive away pests. Some of these compounds scramble the scent receptors insects use to find them. Other plants use scent on its own to scare off pests. Herbs such as basil, rosemary, oregano, mint, and thyme are good examples. We love these tasty, aromatic herbs in our food, but bugs find them repulsive.



Basil has a strong aroma known to repel mosquitoes and flies. Peppermint has a higher concentration of menthol than other kinds of mint, and bugs hate the smell and taste. Rosemary is effective at blocking flies, mosquitoes, and cabbage moths. Boil rosemary in water to make a natural repellent spray. You can also throw a few sprigs of it on your grill at your next barbecue. The rosemary-scented smoke will keep the bugs away.

Essential Oils



Essential oils are powerful potions that plants use to defend themselves. Plants like lavender and lemongrass have essential oils with strong smells that insects can’t stand. Oregano contains an essential oil called carvacrol. Along with garden pests, it can be effective in repelling bed bugs.

Flower Power



You can also use flower power in the battle against bugs. Marigolds and chrysanthemums contain the chemical pyrethrum, which impedes an insect’s nervous system and paralyzes it. Nasturtium is a good choice for companion planting with your vegetables. Many veggie-loving pests hate the smell of these flowers. Same with petunias: A lot of insects hate the smell of this low-maintenance, high-color flower.



What if the pest bugging your lawn or garden is bigger than a bug? Turns out many of the plants we’ve mentioned can also deter pests including rodents, rabbits, and deer. If you’re looking to repel rabbits, try onions and garlic. They’re toxic to rabbits because they contain compounds called thiosulphates and disulfides. These compounds damage a rabbit’s red blood cells and can cause anemia and even death. Rodents and deer will avoid onions and garlic because of the smell. Chop up some garlic and sprinkle it around your edible crops. Plant onions near your leafy greens to keep them safe.

Natural Defenses



Plants also use structural defenses to protect themselves. Bark, thorns, thistles, spikes, and prickles make it hard for pests to attack. Cacti and succulents are good examples. Like most native plants, they’ve developed defenses against local pests. If you’ve ever stepped on one, you’ve experienced the effectiveness of this defense.

While plants won’t take care of all the pests plaguing your lawn and garden, they can help. And this kind of pest removal is much safer than chemical pesticides for your family, pets, and the environment. So the next time you see a pest that bugs you, put down the spray can, pick up a shovel, and start planting.

Richard Gillespie is an exterminator whose interest in household and landscape pests began as a child, when he would crank up the radio to hear “I Don’t Like Spiders and Snakes.” He prides himself on practicing humane and eco-friendly pest control — unless he finds a rat. Then, all bets are off.


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