“What are the best plants and/or flowers to deter insects from a vegetable garden?” Question from Vesta of Fort Oglethorpe, Georgia
Answer: Research has shown that some companion plantings will reduce the number of insect pests that attack specific vegetable crops. These companions fall under two categories: trap crops and insect-repelling companion plants. Trap crops are plantings that attract insect pests, luring them away from favorite vegetables. These take up a lot of space and are not practical for most home gardeners, so I will just cover repellent companion plants that have been shown to really help ward off vegetable pests.
Insect-Repelling Companion Plants
These are plants that emit chemicals that deter insects. Repelling plants will never totally protect vegetables from the pests that attack them, but they can reduce pest numbers. Here are a few good examples of vegetable pests and the companion plants that repel them.
Some culinary herbs have been shown to offer repellent protection to specific veggies. For example, plantings of tall basil (Ocimum basilicum) can reduce the number of tomato hornworms on tomatoes and thrips on flowers. Plant-damaging moths, aphids, and mites may also be repelled by chives and other onion (Allium spp.) relatives. These pests attack a wide host of vegetable plants, such as brassicas (collards, cabbage, broccoli, and cauliflower), beans, and squash, so a border of chives might be really helpful in the garden. Sage (Salvia officinalis), rosemary (Rosmarinus officinalis), hyssop (Hyssop officinalis), thyme (Thymus vulgaris), dill (Anethum graveolens), and chamomile (Chamaemelum nobile) may also provide brassicas some protection against common pests.
Catnip (Nepeta cataria), wormwood (Artemisia absinthium), southernwood (Artemisia abrotanum), and tansy (Tanacetum vulgare) reduce damage by flea beetles, a pest that attacks eggplant, brassicas, tomatoes, and other common crops. One downside is to these repellent plants is that they tend to spread and become weedy. Of these, I recommend catnip the most. Just clip it back occasionally to keep it from flowering and setting seed.
A few common garden flowers also have repelling qualities. Nasturtiums (Tropaeolum majus) may help brassica crops, and marigolds help tomatoes by repelling the tomato root-knot nematode, a debilitating underground pest. (Click here to learn more about how marigolds help tomatoes.)
All of the companion herbs and flowers mentioned will flourish in soil amended with fertilizer-enriched Black Gold Garden Soil. I hope that some of these tips. When planting to protect, it is most helpful to plant a close row or ring of repelling plants near the vegetables that you want to protect.
Black Gold Horticulturist