Common nameScientific nameHelpsHelped byAttractsRepelsAvoidComments
AlliumsAlliumfruit trees, nightshades(tomatoes, capsicum peppers, potatoes), brassicas (cabbage, broccoli, kohlrabi, etc.) carrotscarrotsslugs, aphids, carrot fly, cabbage worms[1]beans, peas, parsleyAlliums include onions, garlic, leeks, shallots, chives, and others
AsparagusAsparagus officinalisTomatoes[2]Aster Family flowers, Dill, Coriander, Tomatoes, Parsley, Basil, Comfrey, Marigoldscoupled with Basil seems to encourage lady bugsOnion, Garlic, Potatoes
BrassicasBrassicapotatoes, cereals (e.g. corn, wheat)geraniums, dill, alliums (onions, shallots, garlic, etc.), rosemary, nasturtium, boragewirewormsmustards, nightshades (tomatoes, peppers, etc.)Brassicas are a family of species which include broccoli, cabbage, Brussels sprouts, kohlrabi, and cauliflower.
BeansPhaseolusCorn (see Three Sisters), Spinach, lettuce, rosemary, summer savory, dill, carrots, brassicas, beets, radish, strawberry and cucumbersEggplant, Summer savouryCalifornia beetlesTomatoes, chili peppers, alliums (onions, garlic, etc.), brassicas (cabbage, broccoli, etc.)Hosts nitrogen-fixing bacteria, a good fertiliser for some plants, too much for others
BeetsBeta Vulgarislettuce, kohlrabi, onions and brassicasCatnip, Garlic, MintRunner or pole beans[2]Good for adding minerals to the soil through composting leaves which have up to 25% magnesium. Runner or pole beans and beets stunt each other's growth.
BroccoliBrassica oleraceageraniums, dill, alliums, rosemary, nasturtium, boragemustards, Tomatoes, peppersRosemary repels cabbage fly, geraniums trap cabbage worms, same general companion profile as all brassica (cabbage, kohlrabi, Brussels sprouts, cauliflower, etc.)
CabbageBrassica oleraceageraniums, dill, alliums, rosemarymustards, Tomatoes, peppers strawberries, and pole/runner beansRosemary repels cabbage flies, geraniums trap cabbage worms, same general companion profile as all brassica (cabbage, kohlrabi, Brussels sprouts, cauliflower, etc.)
CarrotsDaucus carotaTomatoes, Alliums (onions, chives, etc.), lettucealliums (leeks, shallots, etc.), rosemary, wormwood, sage, beans, flaxassassin bug, lacewing, parasitic wasp, yellow jacket and other predatory waspsDill, parsnip, radishTomatoes grow better with carrots, but may stunt the carrots' growth. Beans (which are bad for tomatoes) provide the nitrogen carrots need more than some other vegetables. Aromatic companion plants repel carrot fly. Alliums inter-planted with carrots confuse onion and carrot flies.
CeleryApium graveolensCosmos, Daisies, Snapdragonscorn, Aster flowers, these can transmit the aster yellows disease
Corn / MaizeZea maysbeansSunflowers, legumes (beans, peas, etc.), peanuts, cucurbits (squash, cucumbers, melons, etc.), amaranth, white geranium, lamb's quarters, morning glory, parsley, and potato[2]Tomato, CeleryProvides beans with a trellis, is protected from predators and dryness by cucurbits, in the three sisters technique
CucumberCucumis SativusNasturtiums, radishes, marigolds, sunflowers, peas, beets, carrots, and DillBeneficial for ground beetlesTomato, Sage
Eggplant or AubergineSolanum melongenaBeans, PeppersMarigolds, tarragon, mintsMarigolds will deter nematodes.
LeekAllium ampeloprasum v. porrumCelery, apple treescarrotscabbage worms, aphids, carrot fly, othersLegumes (beans, peas, etc.), Swiss chardSame companion traits as all alliums (onions, garlic, shallots, chives, etc.)
LettuceLactuca sativaRadish, Kohlrabi, beans, carrotscelery, cabbage, cress, parsleyMints (including hyssop, sage, and various "balms") repel slugs, a bane of lettuce and cabbages
MustardBrassicaceae, Sinapis albaCabbage, cauliflower, radish, Brussels sprouts, turnipsvarious pestsSame general companion profile as all brassica (cabbage, kohlrabi, Brussels sprouts, cauliflower, etc.)
NightshadesSolanaceaecarrots, alliums, mints (basil, oregano, etc.)beans, black walnuts, corn, fennel, dill, brassica (broccoli, cabbage, cauliflower, etc.)Nightshade plants include tomatoes, tobacco, chili peppers (including bell peppers), potatoes, eggplant, and others
OnionAllium cepaTomatoes, brassicas (broccoli, cabbage, etc.)Carrotsaphids, carrot fly, other pestsBeans, lentils, peas, parsleySame companion traits as all other alliums (chives, garlic, shallots, leeks, etc.)
PeppersSolanaceae, Capsicumthemselves, marjoramtomatoes, geraniums, petuniasTomato Hornwormbeans, kale (cabbage, Brussels sprouts, etc.)Pepper plants like high humidity, which can be helped along by planting with some kind of dense-leaf companion, like marjoram and basil; they also need direct sunlight, but their fruit can be harmed by it...pepper plants grown together, or with tomatoes, can shelter the fruit from sunlight, and raises the humidity level.
PotatoSolanum tuberosumHorseradishAtriplex, carrot, cucumber, onion, raspberries, squash, sunflower, tomatoHorseradish increases the disease resistance of potatoes
ParsnipPastinaca Sativafruit treesa variety of predatory insectsThe flowers of the parsnip plant left to seed will attract a variety of predatory insects to the garden, they are particularly helpful when left under fruit trees, the predators attacking codling moth and light brown apple moth. The root also contains Myristricin, which is toxic to fruit flies, house flies, red spider mite, pea aphids.
Pumpkin and other SquashCurcurbita sppcorn, beansBuckwheat, catnip, tansy, radishesSpiders, Ground BeetlesRadishes can be used as a trap crop against flea beetles, Curcurbita can be used in the three sisters technique
RadishRafanus Sativussquash, eggplant, cucumber,[2]lettuceflea beetles, cucumber beetlesRadishes can be used as a trap crop against flea beetles
SpinachSpinacia oleraceaPeas, BeansThe peas and beans provide natural shade for the spinach
TomatoesSolanum lycopersicumroses, peppers, asparagusbasil,[3] oregano, parsley, carrots, marigold, Alliums, celery, Geraniums, Petunias, Nasturtium, Borage, any type of onion or chivesTomato Hornwormasparagus beetleBlack walnut, corn, fennel, peas, dill, potatoes, beetroot, brassicas (kohlrabi, cabbage, etc.), rosemaryDill attracts tomato hornworm.
Growing basil 10 inches apart from tomatoes can increase the yield of tomatoes by about 20%.[3]