Companion or co-planting is the idea that placing different plants near each other is beneficial. Planting garlic near certain fruits and vegetables not only gives you a hefty harvest of garlic but also improves the growth of your other plants. Garlic has natural fungicidal and insecticidal properties that keep neighbor plants healthy.
Lettuce, Cabbage and Carrots
When planted near lettuce, garlic will help deter aphids, which suck the juices out of the lettuce leaves. It deters codling moths, Japanese beetles, cutworms, root maggots and snails, all major cabbage pests. And it offends the carrot root fly. Garlic will also help improve flavor of all the members of the cabbage family, including broccoli, Brussels sprouts, kale, kohlrabi and cauliflower.
Beets, Celery and Tomatoes
Garlic improves the growth and flavor of beets and tomatoes, and it deters leaf hoppers and aphids. Garlic also keeps spider mites and Japanese beetles away from tomatoes. Celery is often inundated with leaf miners, and garlic will deter these pests.
Planting garlic near the bases of peach trees will keep away peach borers, a very destructive insect. Trees are most susceptible to this pest when they are young and newly planted. Garlic is also effective in deterring Japanese beetles and aphids from raspberries. Raspberries and peaches should never be planted near each other.
Plants to Avoid
Do not plant garlic near legumes (beans), peas or asparagus. Garlic will stunt their growth.