Companion Planting

Companion planting is probably about 2 parts science to 1 part folklore or wishful thinking. Some plants definitely do benefit from being planted side by side, and conversely, some plant combinations have negative, unwanted results. In other cases, it's not clear where the science meets up with simple tradition. Below is a list of some recommended planting combinations, as well as some tips for attracting pollinators and other beneficial insects.
 

Agastache – Very attractive to bees. Plant a row away from the garden to lure cabbage moths away from Brassica crops. Do not plant near radishes

Alyssum – Very attractive to pollinators, and useful as a mulch to keep weeds down between rows.

Amaranth – Plant with corn to shade the soil and retain water. Attracts predatory ground beetles.

Asparagus – Plant with asters, basil, cilantro, dill, cilantro, marigolds, nasturtiums, oregano, parsley, peppers, sage, and thyme. Asparagus repels nematodes that attack tomatoes, and tomatoes repel asparagus beetles.

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.

Broad beans – Excellent for fixing nitrogen in the soil. Avoid planting near onions.

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.

Soya beans – Good for fixing nitrogen, and acting as a mulch against weeds. Grow with corn. Soya beans repel Japanese beetles and chinch bugs.

Beets – Beets add minerals to the soil. The greens are very good for the compost. 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.

Borage – Excellent all around companion plant. Borage deters tomato hornworm and cabbage worms, and is particularly good planted near tomatoes and strawberries. Very attractive to pollinators, and excellent for the soil and compost. Borage is deer-proof.

Brassicas (broccoli, Brussels sprouts, cabbage, carrots, cauliflower, celery, chervil, chives, collards, cucumber, kale, kohlrabi, pac choi, turnip) – All benefit from chamomile, dill, mint, rosemary, and sage. Avoid planting near eggplants, peppers, potatoes, or tomatoes.

Buckwheat – Fixes calcium in the soil, and makes an exceptionally good green manure plant. Buckwheat absorbs nutrients that are not available to other plants, and can then be composted or tilled under, releasing those nutrients in accessible forms. Flowers are attractive to pollinators as well as beneficial predatory insects: hover flies, pirate bugs, tachinid flies, and lady beetles.

Calendula – Repels a number of bad nematodes in the soil, but may attract slugs. Plant with tomatoes and asparagus.

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. Carrots planted near tomatoes may have stunted roots, but will have exceptional flavour. Chives also benefit carrots.

Catnip – Attracts pollinators (and cats!), but repels aphids, flea beetles, Japanese beetles, ants, weevils, and squash bugs.

Celery – Good partner for beans, Brassicas, cucumber, garlic, leek, lettuce, onion, and tomatoes.

Chamomile – Attracts hoverflies and wasps. Plant near onions to improve their flavour.

Chervil – Excellent companion for Brassicas, lettuce, and radishes, but does best in part shade. Chervil helps to repel slugs.

Chives – Improves the flavour of carrots and tomatoes. A companion plant for Brassicas. Helps to repel aphids, carrot rust fly, and Japanese beetles. Avoid planting near beans and peas.

Chrysanthemum – White flowering mums repel Japanese beetles.

Cilantro – Repels aphids, potato beetles, and spider mites. Plant near cilantro.

Clover – Attracts many beneficials and builds the soil. Helps fight cabbage worms, and increases the number of predatory ground beetles.

Collards – Plant near tomatoes, which repel the flea beetles that so often look for collards to eat.

Corn – Companion to beans, beets, cucumber, dill, melons, parsley, peas, potato, soya beans, squash, and sunflower. Avoid planting next to celery or tomatoes. Amaranth makes a great mulch between rows by competing with weeds and conserving ground moisture.

Cucumber – Plant beside asparagus, beans, Brassicas, celery, corn, dill, kohlrabi, lettuce, onion, peas, radish, and tomatoes. Avoid planting near potatoes and sage. Both corn and sunflowers can act as a trellis for cucumbers to good effect. Dill will help cucumbers by attracting predatory insects, and nasturtiums will improve the flavour and growth of cucumbers.

Dill – Dill improves the health of cabbages and other Brassicas, and is a very good companion for corn, cucumbers, lettuce, and onions. Dill attracts the predatory wasps that feed on garden caterpillars, and it repels aphids and spider mites. Avoid planting near carrots and tomatoes.

Eggplant – A good companion for amaranth, beans, marigolds, peas, peppers, spinach, and thyme. Do not plant eggplants near fennel.

Fennel – Not a companion for any garden food plant, fennel will actually inhibit growth in bush beans, kohlrabi, tomatoes, and others. Plant it, but keep it out of the veggie garden.

Garlic – Planting garlic near roses will help to repel aphids. Because of its sulfur compounds, it may also help repel whiteflies, Japanese beetles, root maggots, carrot rust fly, and other pests. Garlic, made into a tea, or spray, will act as a systemic pesticide, drawing up into the cells of the plants. It’s a good companion for beets, Brassicas, celery, lettuce, potatoes, strawberries, and tomatoes. Avoid planting it near peas or beans of any kind.

Kohlrabi – A worthy companion for beets, Brassicas, cucumbers, and onions. Avoid planting near peppers, pole beans, strawberries, and tomatoes.

Leeks – Grow with beets, carrot, celery, onions, and spinach. Avoid planting near beans and peas. Leeks help repel carrot rust flies.

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. Mexican Marigolds (T. minuta) have the same effect, and may repel rabbits.

Melon – Great companions for corn, marigolds, nasturtiums, pumpkin, radish, squash, and sunflowers. Avoid planting near potatoes. Melon leaves are full of calcium, so they’re good for the compost heap.

Mint – Mint attracts earthworms, hoverflies and predatory wasps, and repels cabbage moths, aphids, and flea beetles. Mint is invasive, so it may be better to use cut mint as a mulch around Brassicas, or to restrain it in containers around the vegetable garden. Avoid planting near parsley.

Nasturtium – These plants make a good trap crop for aphids, and they deter whiteflies, cucumber beetles, and attract predatory insects. It is a good companion for Brassicas, cucumbers, melons, radishes, and tomatoes.

Oats – They grow very quickly for quick tilling to add organic matter to beds, and work well when planted with clover or vetch. An excellent source of green matter for the compost.

Onions – Plant chamomile and summer savory near onions to improve their flavour. Onions also work well alongside beets, Brassicas, carrots, dill, kohlrabi, leeks, lettuce, strawberries and tomatoes. Don’t plant onions near asparagus, onions of any kind, or peas.

Oregano & Marjoram – Oregano is particularly good for repelling cabbage moths, and it can be planted between rows of Brassicas for this purpose. Also good around asparagus and basil.

Parsley – Parsley likes asparagus, carrots, chives, corn, onions, and tomatoes. The leaves can be sprinkled on asparagus to repel asparagus beetles, and around roses, to improve their scent. Parsley allowed to bloom will attract hoverflies and predatory wasps. Don’t plant it near mint.

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.

Potato – Bush beans, Brassicas, carrots, celery, corn, garlic, marigolds, onions, and peas all do well planted near potatoes. Avoid planting potatoes near asparagus, cucumber, kohlrabi, melons, parsnips, rutabaga, squash, sunflower, and turnips.

Radish – Plant radishes 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.

Rosemary – Rosemary is a good companion for beans, Brassicas, and carrots.

Rye – Fall rye gives off a chemical that inhibits the germination of weed seeds. Planted twice in a row, it can choke out several tough weed species for good. It produces masses of useful organic matter for tilling under or adding to the compost.

Sage – Sage repels both the cabbage moth and the carrot rust fly, so it’s a great all around companion plant in the vegetable garden. Do not, however, plant it near cucumbers, which are sensitive to aromatic herbs.

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.

Strawberry – These little plants respond strongly to nearby plants. Couple them with beans, borage, garlic, lettuce, onions, peas, spinach, and thyme. Avoid Brassicas, fennel, and kohlrabi.

Summer Savory – This herb attracts honeybees, and repels cabbage moths. Planting it near beans and onions will improve the flavour of both.

Sunflower – Sunflowers planted near rows of corn are said to increase yields. Aphids may be herded by ants onto sunflowers without causing the plants any harm.

Swiss chard – Beans, Brassicas, and onions make the best companions for chard.

Thyme – An all around beneficial plant for the garden, thyme is particularly worth planting near Brassicas, as it repels cabbage moths, and strawberries, as it enhances flavour.

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. Corn will attract tomato pests, and kohlrabi will stunt tomatoes’ growth. Potatoes may spread blight to tomatoes, so keep them apart. Do no plant tomatoes near walnut trees.

Turnip – Turnips are easygoing, but benefit from mint and pea companions.

Vetch – Vetch has long roots that fix nitrogen in the soil, and provide masses of organic matter for tilling under. Do not let vetch go to seed, as it will come back strongly. The seeds are toxic to chickens.

Yarrow – Its scent repels aphids, but attracts hoverflies, lady beetles, and wasps that prey on garden grubs. The leaves and stems of yarrow contain enzymes that break down rapidly, so it can be added to the compost raw or as a tea to accelerate the heap.