Companion Planting

Nitrogen Fixers

Nitrogen fixers are commonly planted as companion plants for their ability to convert atmospheric nitrogen into forms in the soil usable by other plants.

For maximum nitrogen returned to the soil, plant nitrogen fixers as cover crops that you chop and drop as mulch when at maximum flower, when the vegetation is at its maximum nitrogen content.

Examples include:

1. most legumes (Fabaceae - eg. clover, beans, alfalfa)

2. azolla (mosquito fern - Salviniaceae)

3. genus Trema (Cannabaceae)

4. actinorhizal plants that form a symbiosis with actinobacteria Frankia

Betulaceae

- genus Alnus (alder)

Coriariaceae

- genus Coriaria

Myricaceae

- genus Comptonia (sweetfern)

- genus Myrica (bayberry)

Elaeagnaceae

- genus Elaeagnus (silverberry/oleaster)

- genus Hippophae (sea buckthorns)

- genus Shepherdia (buffaloberry)

Rhamnaceae

- genus Colletia

- genus Discaria

- genus Kentrothamnus

- genus Retanilla

- genus Trevoa

- genus Ochetophila

- genus Ceanothus

Rosaceae

- genus Cercocarpus (mountain mahoganies)

- genus Chamaebatia (mountain miseries)

- genus Dryas

- genus Purshia (bitterbrushes)

5. cycads

6. genus gunnera (Gunneraceae)

7. some lichens, liverwort, and hornworts

Trap Crops

Trap crops are plants used as distractions for pests to protect more valuable crops.

1. alfalfa planted alongside cotton to draw away lygnus bugs, or planted in strips alongside tobacco to protect from heliothis

2. chervil protects from slugs

3. Soybeans protects by rye (protects from corn seeding maggots), sesbania (protects from stink bugs), sicklepod (protects from velvet green caterpillars)

4. mustard planted near strawberries protects from lygnus bugs

5. blue hubbard squash planted near cucurbits protect them from squash vine borers and cucumber beetles

Host-finding disruption

Any green ground cover confuses pests which must make a certain number of "appropriate landings" on their host plant before laying eggs. If they make too many inappropriate landings, they leave the area.

eg. clover ground cover

Beneficial "weeds"

1. mimosa pudica - attracts predatory beetles

2. Euphorbia lathyris - repels moles

3. urtica dioica - young leaves are edible and can attract beneficial insects

4.Allium vineale - repels slugs, aphids, carrot fly, and cabbage worms. Can be used as conventional chives. Do not plant with beans, peas, or parsely.

5.Brassicas - attract ladybugs and traps brassica pests including aphids

6. Rosa - deter rodents and deer, and trap Japanese beetles

7. Borago officinalis - attract predatory wasps

8. Taraxacum (dandelion) - attract pollinators and large tap root breaks up soil and transports nutrients from the deep soil to the surface

9. Trifolium (clover) - flowers attract pollinators. Do not plant near tomatoes, which prefer a mild nityrogen deficit in the soil.

10. neem - repels insects

11. blackberry - edible and may deter large mammals, attracts predatory insects

12. burdock - roots, stalks, and young leaves are edible

13. Stellaria media - edible and grows as ground cover

14. Centaurea cyanus - edible

15. Hypochaeris radicata - leaves are edible raw, roots are edible after being roasted

16. Equisetum (horsetail) - tops can be eaten like asparagus

17. Chenopodium berlandieri - leaves and shoots edible raw, prevents erosion, distracts leaf miner pests

18. Portulaca oleracea - edible (raw or sauteed)

19. Capsella bursa-pastoris - leaves are edible

20. Nasturtium officinale - can be eaten raw or cooked, but may contain potentially-fatal liver fluke

21. Leonurus cardiaca - attracts bees

22. Eutrochium - attracts pollinators and predatory insects

23. genus Aster - attract predatory insects

24. Vigna unguiculata (cowpea) - attracts ladybird beetle

25. Solanaceae - breaks up hardpan

Other beneficial plants

1. Artemisia - repels ants, cabbage looper, cabbage maggot, carrot fly, codling moth, flea beetles, whiteflies, the Cabbage White, and the Small White, as well as mice

2. basil - repels flies and mosquitoes, the carrot fly, asparagus beetles and whiteflies

3. borage - repels tomato hornworm and cabbage worms

4. catnip - repels ants, flea beetles, aphids, the Japanese beetle, squash bugs, weevils, the Colorado potato beetle, the cabbage looper, and cockroaches

5. chamomile - repels flying insects

6. chives - repels carrot fly, Japanese beetle and aphids

7. chrysanthemums - repel roaches, ants, the Japanese beetle, ticks, silverfish, lice, fleas, bedbugs, and root-knot nematodes

8. citronella - repels insects and deters cats

9. clover - repels aphids and wireworms

10. Lantana camara - repels mosquitoes

11. coriander - repels aphids, Colorado potato beetle, and spider mites

12. cosmos - repel corn earworm

13. Fritillaria imperialis - repel rabbits, mice, moles, voles and ground squirrels

14. dahlias - repel nematodes

15. dill - repels aphids, squash bugs, spider mites, the cabbage looper, and the Small White

16. eucaluptus - repel aphids, the cabbage looper, and the Colorado potato beetle

17. fennel - repels aphids, slugs, and snails

18. Lantana ukambensis - repels mosquitoes

19. Mirabilis - attracts and kills Japanese beetles

20. garlic - repels root maggots, cabbage looper, Mexican bean beetle, and peach tree borer

21. geraniums - repel leafhoppers, the corn earworm, and the Small White

22. Hyssopus officinalis - repels the cabbage looper and the Small White

23. Delphinium - repels aphids

24. lavender - repels moths, scorpions, water scorpions, fleas, and flies, including mosquitoes

25. leek - repel carrot flies

26. lemongrass - repel mosquitoes

27. Melissa officinalis - repel mosquitoes

28. Thymus citriodorus - repel mosquitoes

29. lettuce - repels carrot fly

30. Ocimum americanum - repels mosquitoes

31. myrrh - repels insects

32. narcissus - repels moles

33. nasturtiums - repel squash bugs, aphids (though there is conflicting information with some sources stating it attracts aphids), many beetles, and the cabbage looper

34. onion - repels rabbits, the cabbage looper, and the Small White

35. oregano - repels many pests

36. parsley - repels asparagus beetles

37. peppermint - repels aphids, cabbage looper, flea beetles, squash bugs, whiteflies, and the Small White

38. petunias - repel aphids, tomato hornworm, asparagus beetles, leafhoppers, and squash bugs

39. carnivorous plants - trap and kill insects

40. radish - repels cabbage maggot and cucumber beetles

41. rosemary - repels cabbage looper, carrot fly, cockroaches and mosquitoes, slugs, snails, as well as the Mexican bean beetle

42. Salvia yangii - repels wasps

43. rue - repels cucumber and flea beetles

44. Sarracenia pitcher plants - particular adept at trapping yellowjackets

45. spearmint - repels fleas, moths, ants, beetles, rodents, aphids, squash bugs, and the cabbage looper

46. Amaranthus spinosus - repels cutworms

47. Collinsonia canadensis - repels mosquitoes

48. Satureja hortensis - repels bean beetles

49. Tanacetum vulgare - repels ants, many beetles and flies, squash bugs, cutworms, Small White, and Cabbage White

50. Thymus vulgaris - repels cabbage looper, cabbage maggot, corn earworm, whiteflies, tomato hornworm, and Small White

51. Nicotiana tabacum - repels carrot fly, flea beetles and worms

52. tomato - repels asparagus beetles

If you have this pest, use...

Ants: Artemisia, catnip, chrysanthemums, spearmint, Tanacetum vulgare

Cabbage Looper: Artemisia, catnip, dill, eucalyptus, garlic, Hyssopus officinalis, nasturtiums, onion, peppermint, rosemary, spearmint, Thymus vulgaris

Cabbage Maggot: Artemisia, radish, Thymus vulgaris

Root maggots: garlic

Carrot fly: Artemsia, basil, chives, lettuce, rosemary, Nicotiana tabacum, leeks

Codling moth: artemisia

Flea beetles: artemisia, catnip, peppermint, rue, Nicotiana tabacum

Whiteflies: Artemisia, basil, peppermint, Thymus vulgaris

Cabbage White: Artemisia, Tanacetum vulgare

Small white: Artemisia, dill, geraniums, Hyssopus officinalis,

onion, peppermint, Tanacetum vulgare, Thymus vulgaris

Mice: Artemisia, Fritillaria imperialis

Flies: basil, lavender, Tanacetum vulgare

Mosquitos: basil, Lantana ukambensis, Lantana camara, lavender, lemongrass, Melissa officinalis, Thymus citriodorus, Ocimum americanum, rosemary, Collinsonia canadensis

Asparagus beetles: basil, parsely, petunias, tomato

Hornworm: borage, petunias, Thymus vulgaris

Aphids: catnip, chives, clover, coriander, dill, eucalyptus, fennel, Delphinium, Nasturtiums (conflicting information), peppermint, petunias, spearmint, marigolds

Japanese beetle: catnip, chives, chrysanthemums, Marabilis

squash bugs: catnip, dill, Nasturtiums, peppermint, petunias, spearmint, Tanacetum vulgare

Weevils: catnip

Potato beetle: catnip, coriander, eucalyptus

Cockroach: rosemary, catnip, chrysanthemums

Ticks: chrysanthemums

Silverfish: chrysanthemums

Nematodes: chrysanthemums, dahlias

Fleas: chrysanthemums, lavender, spearmint

Wireworms: clover

Worms: Nicotiana tabacum

Spider mites: coriander, dill

Corn earworm: cosmos, geranium, Thymus vulgaris

Moths: lavender, spearmint

Scorpions: lavender

Rabbits: Fritillaria imperialis, onion

Slugs & snails: fennel, rosemary

Mexican bean beetle: garlic, rosemary, Satureja hortensis

Peach tree borer: garlic

Leafhoppers: geranium, petunias

Cucumber beetles: radish, rue

Wasps: Salvia yangii, Sarracenia pitcher plants

Cutworms: Amaranthus spinosus, Tanacetum vulgare

cabbage looper

root maggot

carrot fly

codling moth

flea beetle

white fly

cabbage white

small white

asparagus beetle

hornworm

Japanese beetle

squash bug

weevil

potato beetle

silverfish

nematodes

nematode

wireworms

spider mites

corn earworm

Mexican bean beetle

peach tree borer

peach tree borer damage

leafhopper

cucumber beetle

cutworm

Plant Combinations to Avoid

Some plants inhibit the growth of others, either through soil chemical means or by attracting pests. Avoid these combinations.

Alliums (onions, garlic, leeks, shallots, chives): Beans and peas

Asparagus: onion, garlic, potatoes, gladiolus

Bush Beans: fennel, soybeans, dry beans, alfalfa

Pole Beans: sunflowers, beets, brassicas, kohlrabi

Beets: runner or pole beans

Brassicas: mustards, nightshades (tomatoes, peppers), pole beans, strawberries

Cabbage: grapes

Carrots: dill, parsnip, radish

Celery: corn, asters

Corn: tomatoes, celery

Cucumber: potato, aromatic herbs (Lamiaceae - mint family)

Leek: Swiss chard

Legumes: Alliums, gladiolas

Lettuce: celery, cabbage, cress, parsley

Solanums (nightshade family - tomatoes, peppers): beans, black walnuts, corn, fennel, dill, brassicas

Onion: lentils, peas

Peppers: beans, kale (cabbage, Brussels sprouts)

Potato: atriplex, carrot, cucumber, pumpkin, raspberries, squash, sunflower, tomato

Pumpkin: potatoes

Radish: grapes

Tomatoes: black walnut, alfalfa, corn, fennel, peppers, peas, dill, potatoes, beetroot, brassicas, rosemary

Turnips/rutabagas: hedge mustard, knotweed

Apple: cedar, walnut

Apricot: peppers

Blueberries: tomatoes

Grapes: cabbage, garlic, radishes

Passion fruit: cucurbits, maize, cowpea, sorghum, okra, sweet potatoes

Strawberries: brassicas, (Verticilium-susceptible species) tomatoes, potatoes, eggplant, peppers, melons, okra, mint, bush or bramble fruits, stone fruits, chrysanthemums, roses

Basil: common rue, thyme

Caraway: dill

Chervil: radish

Chives: beans, peas

Dill: carrots, tomatoes

Fennel: almost everything

Flax: almost everything

Garlic: cabbage, grapes

Hyssop: radish

Lovage: rhubarb

Parsley: alliums, lettuce

Sage: Alliums, common rue

Geraniums: tomatoes, tobacco, eggplants, other nightshades

Lupin: tomatoes and other nightshades

Nasturtium: cauliflower

Sunflower: pole beans

Alfalfa: tomatoes and beans

Walnut: apple, grasses