Basil – Will improve vigour and flavour of tomatoes, planted side-by-side. Also good with asparagus, oregano, and peppers. Basil helps repel flies, mosquitoes, and thrips.
Bush & Pole beans – All beans fix nitrogen in the soil. Plant with beets, brassicas, carrots, celery, chard, corn, cucumber, eggplant, peas, potatoes, radish, and strawberries. Avoid planting near chives, garlic, leeks, and onions. Pole beans and beets stunt each other’s growth.
Beets – Beets add minerals to the soil. Plant with bush beans, brassicas, corn, garlic, kohlrabi, leeks, lettuce, and mint. Add cut mint leaves as a mulch for beets. Avoid planting beets near pole beans.
Brassicas (broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, turnip) – benefit from chamomile, dill, mint, rosemary, and sage. Avoid planting near eggplants, peppers, or tomatoes.
Carrots – Plant with beans, brassicas, chives, leeks, lettuce, onions, peas, peppers, pole beans, radish, rosemary, sage, and tomatoes. Avoid planting with dill, parsnips, and potatoes.
Cucumber – Plant beside asparagus, beans, brassicas, celery, corn, dill, kohlrabi, lettuce, onion, peas, radish, and tomatoes. Avoid planting near potatoes and sage. Dill will help cucumbers by attracting predatory insects, and nasturtiums will improve the flavour and growth of cucumbers.
Leeks – Grow with beets, carrot, celery, onions, and spinach. Avoid planting near beans and peas.
Lettuce – Good companions for beets, brassicas, carrot, celery, chervil, cucumbers, dill, garlic, onions, radish, spinach, squash, and strawberries.
Marigold – French Marigolds (Tagetes patula) produce chemicals that kill nematodes and repel whitefly. Avoid planting them near beans.
Peas – Superb companions for beans, carrots, celery, corn, cucumber, eggplant, parsley, peppers. potatoes, radish, spinach, strawberries and turnips. Avoid planting peas near onions.
Peppers – Pepper plants make good neighbours for asparagus, basil, carrots, cucumbers, eggplant, endive, oregano, parsley, rosemary, squash, Swiss chard, and tomatoes. Never plant them next to beans, brassicas, or fennel.
Radish – Plant near beans, beets, celeriac, chervil, cucumber, lettuce, mint, parsnip, peas, spinach, squash, and tomatoes. Avoid planting near agastache or potatoes. It is said that planting 3 or 4 icicle radishes around the mound where you plant squash, and allowing them to grow and bloom, will prevent most pests of squash and cucumber.
Spinach – A good companion for brassicas, eggplants, leeks, lettuce, peas, radish, and strawberries. Particularly don’t plant spinach near potatoes.
Squash – Companions: corn, lettuce, melons, peas, and radish. Avoid planting near brassicas or potatoes. Borage is said to improve the growth and flavour of squash. Marigolds and nasturtium repel numerous squash pest insects.
Tomatoes – Another sensitive plant when it comes to companions, tomatoes benefit from asparagus, basil, beans, borage, carrots, celery, chives, collards, cucumber, garlic, lettuce, marigold, mint, nasturtium, onion, parsley, and peppers. Avoid planting alongside brassicas and dill.