Growing vegetables and ornamental plants often means doing battle with a variety of invaders out to devour your crops and flowers. Synthetic pesticides may be potent, but many gardeners are understandably apprehensive to spray poison around, especially on produce they hope to harvest and serve at the family table. One natural, eco-conscious alternative to chemical commercial products is good old garlic (Allium sativum).
Simply cultivating the so-called “stinking rose” among other plants can thwart pests, while a spray made from crushed garlic cloves can be even more successful. Ahead, learn why garlic works, which pests it can send packing, and how to easily prepare effective formulas to control offenders in the garden and inside the house as well.
How Does Garlic Put Off Pests?
Sure, it adds terrific flavor to lots of foods but, as anyone who’s ever recoiled from a companion’s garlic breath knows, this stuff is unpleasantly pungent. The awful odor is due to allicin, a sulfur-containing compound found in garlic, which has both insecticidal and fungicidal properties. As garlic grows, its allicin protects it from pests and, as research has shown, that same malodorous essence can defend other plants.
Apply garlic to plants and they’ll absorb the allicin, which functions as a repellent. The scent is too faint to bother humans, but a host of pests will detect it and steer clear. In addition to being an effective deterrent, garlic may also act as a contact insecticide, outright killing pests when sprayed directly on them.
Which Pests Does Garlic Deter?
Garlic is an effective weapon against some of the most pernicious flying and crawling garden nuisances, including aphids, mites, ticks, nematodes, caterpillars, beetles, and slugs. Indoors, garlic can be used to give ants, roaches, and other pantry pests the heave ho.
Keep in mind, however, that garlic is an all-purpose repellent, so it might also make beneficial bugs take off. Some nematodes (a.k.a. roundworms), for example, help break down compost and attack certain garden pests (such as weevils). But garlic will indiscriminately ward them off along with other species. Pollinators aren’t crazy about garlic either, so take care to use it on foliage only, not directly on flowers, to ensure your garden remains welcoming to birds, bees, and butterflies.
As for four-legged pests, rabbits are allergic to garlic so they typically avoid it and deer don’t care for it either. However, gardeners find that a one-two punch—planting garlic combined with regular application of a garlic spray—is the best defense against these critters. Also note the ASPCA’s warning that garlic (along with onions and chives) is toxic to cats and dogs; use it with caution in any places where house pets may gain access.
Bear in mind, too, that one intrepid insect, the allium leaf miner (Phytomyza gymnostoma), is actually drawn to garlic (and its cousins in the allium family, like onions, shallots, and scallions); the larvae are particularly destructive. Using row covers or netting to protect plants, along with adding sticky traps, can help keep allium leaf miners from menacing garlic in the garden.
What Are the Best Ways to Use Garlic Against Pests?
Here are a few useful tips for arming yourself with allicin to deter destructive insects.
Grow your own garlic
The best defense is often a good offense, so when planning your garden, remember to sow some garlic among other plants. Known as intercropping or companion planting, this practice can help vulnerable crops stave off damage. It’s especially effective when done with veggies that have similar soil and care needs to garlic—full sun and moist yet well-drained conditions. Carrots and beets are ideal, plus they’re low growing, so they won’t steal sunlight from your higher-reaching garlic plant.
Make a garlic spray
Peel and crush six garlic cloves into a pot with two quarts of water on the stove. To amp up the repellent power, add about a tablespoon of hot chili powder or hot sauce, which critters and crawlies also hate. Simmer for 15 minutes or so. Meanwhile, add a squirt of dish soap or cooking oil to a large spray bottle (this will help the garlic spray adhere to foliage.) Let cool, then strain the garlic-chili solution through cheesecloth into the spray bottle. To use, shake well and spray plants weekly, making sure to get the underside of leaves, where insects often lay eggs.
Scatter garlic cloves
Indoors, garlic can combat the likes of ants, roaches, and mealworm beetles (known to wreak havoc on pantry staples like grains and pasta). Garlic is particularly potent against ants, as the strong smell inhibits their ability to recognize their own pheromone trails. Spraying crevices and surfaces with the garlic formula detailed above ought to work well, but simply scattering peeled cloves or even sprinkling garlic powder in cabinets and behind appliances can prove a decent deterrent too. Just be sure curious dogs and cats can’t poke around these areas, since garlic will likely make them sick.
