Infestations of harmful insects are the bane of any gardener’s existence. There is nothing quite so disappointing to come to the garden one morning and find holes chewed into the leaves or stems of vegetables and ornamentals you have been painstakingly cultivating from seed.
While there are several different methods to controlling insects in your garden, a number of them have drawbacks. Chemical insecticides not only introduce toxins to the garden, they may be passed on to you or anyone else who eats the vegetables you grow. Chemical insecticides are also not sustainable in the sense that they do not help to create an ecological balance in the garden. A truly healthy garden grows best when it reflects the natural world’s checks and balances. Insecticides, whether organic or inorganic, also do not discriminate between harmful insects and beneficial ones — the insects which will patrol your garden and devour unwanted intruders.
There are a number of fragrant, attractive, and edible plants and herbs that you can grow in your garden which will act as a deterrent for the vast majority of insect pests. They will not keep harmful insects out of your garden altogether, but if they are planted in tandem with the vegetables and ornamentals you want to protect, they will go a long way to keeping pests away from your prize plants.
The technique of planting deterrent plants among those you wish to protect is part of a strategy called companion planting. Companion planting is quite simply the practice of growing plants together that benefit one another. Certain techniques involve planting vegetables that take nitrogen from the soil with those that return it to the soil; planting tall plants like sunflowers with climbing vegetables like beans, to act as natural trellises; and, as discussed here, planting fragrant herbs and flowers among vegetables and ornamentals to protect them from pests.
What follows is a list of deterrent plants, along with those insects they best repel along with care instructions. It is best to plant a mix of deterrents for any pests you wish to keep at bay. A balanced mix of deterrent plants will act as a strong repellant to pests. Individual vegetables can be ringed with deterrent plants, or you can alternate vegetables with deterrents. In addition to this, it is wise to border your garden beds with a row or two of deterrent plants.
| Deterrent plant | Pests repelled | Planting and care |
| Mint, spearmint | Ants, Aphids, Cabbage maggots, Mice | Plant in full sun and water regularly. Pick mint leaves regularly to encourage vigorous growth. |
| Garlic | Aphids, Japanese beetles, Mites, Plum curculio, weevils | Soak individual cloves before planting. Plant in full sun and water moderately. |
| Marigold | White flies, Tomato hornworms, Eelworms, Nematodes, Mexican bean beetles | Start seeds indoors before last frost. Transplant seedlings two to four weeks after the frost partial to full sun in well-drained soil. Prune flowers regularly to promote robust growth. |
| Geraniums | Japanese beetle, Leafhoppers, Rose chafers | Plant seedlings in full to moderate sun. Water moderately. Prune flowers regularly to promote robust growth.Bring indoors to overwinter in zones 7 and below. |
| Nasturtium | Aphids, Cabbage moth, Squash bugs, Striped pumpkin beetle, Whiteflies | Plant in full sun in well drained soil. Water moderately. Prune flowers regularly to promote robust growth. |
| Rosemary | Cabbage maggot, Cabbage moth, Carrot fly, Mexican bean beetle, Slugs and snails (Prostate Rosemary in particular) | Plant in full sun in well drained soil. Water moderately. Prune tops as buds appear, and bring indoors to overwinter in zones 7 and below. |
| Petunia | Aphids, Leafhopper, Mexican bean beetle, Rose chafer, Squash bug | Plant in full sun in well drained soil. Water moderately. Prune flowers regularly to promote robust growth. |