Companion Plants – Increase Biodiversity

An informed appreciation of companion plants plays a big role in choosing the best plants for vegetable garden.

What is Companion Planting?

Companion planting is the practice of growing particular plants close to one another so that they can benefit from each other’s traits and nutrients. For example:

Attract Pollinators

In order to attract helpful insects to your vegetable garden, include some blooming herbs or annuals. Cucumbers and zucchini, for example, have both male and female flowers and require a visit from a bee or another pollinator to transport pollen from the male to the female flower so that fruit may grow.

Consider planting flowers like Calendula, Cosmos, Alyssum, Coreopsis, Echinacea, Marigolds, Violas and Zinnias at the edges of your garden beds to attract pollinators and add colour.

Inversely, Repel insects

See Companion Plants that repel insects.

Companion Plant Chart

About the companion plants chart: Certain flowers and herbs are frequently listed as good companions for crops. This is usually because they are excellent at deterring pests (see the previous post). Cabbage family = Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Chinese Cabbage, Kale, Kohlrabi. In some cases, companion plants are known to improve flavor or on the flip side, stunt growth.

The chart below is not definitive – while these are the most common companion planting combinations, there are others. We’ve used multiple sources for this list and only added the companion plants when the lists agreed with one another.
Source: Various, including here

Crop	Companion	Don’t Plant With
Amaranth	Corn, Onion, Potato	Broccoli and other Brassicas
Artichokes, Cardoon	Brassicas, Cucumbers, and Prostrate Cucurbits	Potatoes
Asparagus	Basil, Cilantro, Parsley, Tansy, Tomato, Comfrey	Alliums
Basil	Most Vegetables	Rue
Beans	Most Vegetables, Herbs, Marigolds, Tansy	Garlic, Onion, Shallots, Gladiolas
Bush Beans	Beets, Cabbage, Carrots, Catnip, Cauliflower, Corn, Cucumber, Marigolds, Strawberry, Celery, Potatoes, Summer Savory	Fennel, Garlic, Leeks, Onions, Shallots, Sunflowers
Pole Beans	Corn, Marigolds, Potatoes, Radish, Summer Savory,	Allium, Beets, Garlic, Kohlrabi, Leeks, Onion, Shallots, Sunflower
Beets, Chard	Brassicas, Alliums, Bush Beans, Cabbage, Cauliflower, Chard, Garlic, Kohlrabi, Lettuce, Onion	Charlock, Pole Beans
Blackberries	Grapes, Tansy	Raspberries* (blackberries will overwhelm the raspberries)
Blueberries	Clover, Strawberries, Yarrow	Tomatoes
Borage	Squash, Strawberries, Tomatoes
Broccoli, Brussels Sprouts	Beets, Buckwheat, Calendula, Carrots, Catnip, Chamomile, Dill, Hyssop, Marigolds, Mints, Nasturtiums, Onions, Rosemary, Sage, Thyme, Wormwood	Strawberries
Cabbage Family (Brassicas)	Allium, Aromatic Herbs, Beets, Broccoli, Brussels Sprouts, Catnip, Celery, Chamomile, Chard, Clover, Cucumber, Dill, Garlic, Hyssop, Lettuce, Mint, Nasturtium, Onion, Potato, Rosemary, Sage, Southernwood, Spinach, Tansy, Thyme	Pole Beans, Strawberries, Tomato
Cantaloupe	Corn
Carrots, Parsnip	Allium, Beans, Cabbage, Chives, Early Potatoes, English Pea, Leeks, Lettuce, Onions, Peas, Peppers, Radishes, Rosemary, Sage, Salsify, Tansy, Tomato, Wormwood	Dill, Fennel
Celery	Allium & Brassicas, Bush Beans, Chives, Garlic, Nasturtium, Tansy, Tomato
Chives	Apples, Berries, Carrots, Grapes, Peas, Roses, Tomatoes
Corn	Beans, Cucumber, Early Potatoes, English Pea, Marigold, Melons, Parsley, Potato, Peas, Pigweed, Pumpkins, Soybeans, Spinach, Squash, Swiss Chard, Tansy, White Geranium	Tomato
Cowpea	Beans, Carrots, Corn, Cucumbers, Radishes, Turnips	Garlic, Onions, Potatoes
Cucumber	Beans, Cabbage family, Corn, Early Potatoes, English Pea, Marigold, Nasturtium, Oregano, Radish, Sunflowers, Tansy, Tomato	Potato, Sage
Dill	Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Cucumber, Lettuce, Onions, Tomatoes	Carrots
Eggplant	Basil, Beans, Catnip, Lemon Grass, Marigold, Peppers, Potatoes, Tomatoes
Fennel	Nothing	Everything
Garlic	Cabbage, Cane fruits, Fruit trees, Roses, Tomatoes	Peas, Beans
Ginger	Basil, Tomatoes
Gourds	Corn, Sunflowers
Grapes	Basil, Beans, Chives, Clovers, Mustard, Oregano, Peas	Cabbage
Kale	Aromatic Herbs, Buckwheat, Cabbage family, Catnip, Hyssop, Marigolds, Nasturtiums, Rosemary, Sage, Thyme	Pole Beans, Strawberries
Kohlrabi	Allium, Aromatic Herbs, Beets, Broccoli, Brussels Sprouts, Celery, Chamomile, Chard, Clover, Spinach, Thyme	Fennel, Pole Beans, Tomatoes
Lettuce	Beets, Cabbage family, Carrot, Chives, Cucumber, Garlic, Onion, Parsnips, Radish, Strawberry, Tansy	Cabbage family
Marigolds	All crops	nothing
Marjoram	All crops	nothing
Melons	Amaranth, Beans, Chamomile, Corn, Marigold, Oregano, Pumpkin, Radish, Squash	Brassicas
Mustard	Alfalfa cover crops, Fruit trees, Grapes, Legumes
Nasturtiums	Apples, Beans, Cabbage family, Greenhouse crops, Potatoes, Pumpkins, Radishes, Squash
Onion (Allium)	Beets, Brassicas, Cabbage family, Carrot, Chamomile,, Chard, Lettuce, Parsnips, Pepper, Pigweed, Strawberry, Summer Savory, Tomato	Beans, Peas
Okra	Peppers, Squash, Sweet Potatoes	Beans, English Peas
Oregano	All crops
Parsley	Asparagus, Corn, Roses, Tomato
Parsnips	Onions, Radishes, Wormwood
Pea	Beans, Carrots, Chives, Corn, Cucumbers, Early Potatoes, Mint, Radish, Tansy, Turnip	Garlic, Leeks, Onions, Shallots
Peanut	Eggplant, Melon, Squash, Sunflower	Allium, Gladiolus, Irish Potato
Peppers	Basil, Carrots, Clover, Eggplant, Marjoram, Onions, Parsley, Tansy, Tomato	Brassicas, Fennel, Kohlrabi
Potatoes	Basil, Beans, Brassicas, Cabbage family, Corn, Eggplant, Flax, Horseradish, Hemp, Marigolds, Peas, Squash	Apples, Birch, Cherries, Cucumbers, Pumpkins, Raspberries, Sunflowers, Tomatoes, Walnuts
Pumpkins	Corn, Marigold, Melon, Nasturtium, Oregano, Squash	Beans, Cucumbers, English Peas, Sunflower, Tomatoes, Rosaceae
Purslane	Basil, Beets, Cabbage, Carrots, Corn, Lettuce, Turnips, Radish	Beans, English Peas
Radishes	Bean, Carrot, Catnip, Chervil, Cucumbers, Hyssop, Lettuce, Melons, Nasturtiums, Peas, Root crops, Rosemary, Sage	Hyssop, Potato
Rosemary	Beans, Cabbage, Carrots
Sage	Cabbage family, Carrots, Tomatoes
Soybeans	Corn, Potatoes
Spinach	Cabbage family, Celery, Cauliflower, Eggplant, Fave Bean, Strawberries	Hyssop
Squash	Borage, Corn, Marigold, Melon, Nasturtium, Oregano, Pumpkin
Strawberries	Borage, Bush beans, Cabbage, Lettuce, Onion, Pyrethrum, Caraway, Spinach, Thyme	Cabbage family, Potato
Sunflowers	Beans, Corn, Cucumbers, Melons, Peanut	Potatoes
Sweet Potato	Okra, Peppers, Sunflower	Sorghum, Johnson Grass
Swiss Chard	Bush beans, Kohlrabi, Onions	Pole Beans
Tarragon	All crops
Thyme	All crops
Tomatoes	Alyssum, Asparagus, Basil, Bee Balm, Borage, Cabbage family, Carrots, Celery, Chives, Calendula, Dill (until mature), Gooseberries, Marigold, Mint, Mustard, Nasturtium, Onion, Parsley, Pepper, Rosemary, Sage, Stinging Nettles, Tansy	Corn, Fennel, Kohlrabi, Mature Dill, Pole Beans, Potatoes, Walnuts
Turnips and Rutabagas	Catnip, Hyssop, Peas, Catnip, Rosemary, Sage	Cabbage, Fennel, Knotweed, Mustard, Potato
Watermelon	Nasturtium, Marigold	Potato, Mustard

A Summary of the Objectives of Companion Planting

Trap cropping

Using one plant to “capture” insects which are harmful to another plant.

Nitrogen fixation:

Planting legumes like beans, peas, and clover amid nitrogen heavy feeders like corn or potatoes to restore nitrogen to the soil. Legumes derive their nitrogen from the air, not the soil.

Weed suppression:

Plants such as squash, with their large foliage, shade out weeds and cool the roots among tall plants like corn and sunflowers.

Improvement of the soil in the root zone:

Perhaps deciduous trees shade your lettuce and spinach late in the day. The trees also provide nutrients in the form of autumn leaves and carbon, which helps the soil retain moisture. When clover is planted around broccoli, it keeps the soil moist and cool, enhancing broccoli’s growth.

Insect control:

Certain plants produce chemicals from their roots or aerial parts that repel pests. For instance, it is well-documented that the roots of marigolds repel pest nematodes.

Spatial interactions:

Tall-growing plants like sunflowers can shade low growing, shade-tolerant spinach. When corn is planted with squash, it is believed that the prickly vines of squash dissuade raccoons from eating the corn.

Reduced plant diseases:

When peas and grains are planted together, Asochyta blight is significantly reduced. The grain crop modifies the canopy microclimate, making it less humid and reduces the raindrop splash effect, by which the blight spores are spread.

Beneficial insect habitats:

Companion plants can provide a desirable environment for beneficial insects, arthropods, and predatory species like ladybird beetles, lacewings, spiders, predatory wasps, and predatory mites which help keep insect populations in check.