Companion Planting

Companion planting is the practice of combining plants in ways that produce extra benefits for one or both. It is an aspect of IPM (Integrated Pest Management) and is rapidly becoming one of the keys to successfully growing commercial cannabis in an organic fashion. There are 5 main reasons companion planting is used. They are:

 
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1. trap cropping

Examples are planting peas or buckwheat in or near the cannabis. Aphids are attracted to those plants more than the cannabis. Trap crops are good warning indicators for when pests emerge as a potential problem, they let you then engage other IPM practices, like biocontrols, without having the pests ever touch the cannabis plant.

In this photo you can see the swarm of black aphids on the buckwheat leaf in the bottom half of the picture.  At this point the aphid population was not being treated and eventually the aphids made their way to the cannabis plant. Had the problem been dealt with early on with proper biocontrols, the aphids would have been eradicated never even touching the cannabis plant.

 
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2. Symbiotic Nitrogen Fixation

Legumes can “fix” atmospheric nitrogen thus improve the fertility of the soil. Examples are using cover crops of clover, alfalfa or vetch in raised beds or planting peas and cannabis together and then mulching the peas over before they get too high.

In this photo, a 4' x 16' raised bed outside the greenhouse served as an early season pea crop from March-May. The peas were harvested and the stalks were "chopped and dropped".  Full term cannabis plants were planted in June and the rhizobacteria generated from the peas helped harvest additional nitrogen to supplement the cannabis.

 
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3. biochemical pest suppression

The companion plant releases a chemical that mimics a fright or scatter hormone of an unwanted pest thus repelling it. At the same time, that chemical attracts beneficial insects. An example is the Marigold which repels aphids but attracts Hover flies whose larvae feed on aphids. Thyme, Oregano and Rosemary are also great for biochemical suppression.

This photo highlights a long border of oregano seen on the right side of this photo. The oregano acts as a border between the cannabis garden and the vegetable garden, providing biochemical suppression to repel unwanted pests form migrating across that boundary.

 
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4. Physical/Spatial Interactions

Planting in levels to produce more food in less space. An example would be planting potatoes with cannabis to manage symphalyns.

This photo shows a test plot where squash was planted with cannabis. In this case the squash began growing so large that it began to almost outgrow this low growing cannabis strain (pineapple kush) and compete for nutrients. Suppplemental dry amendments were added to compensate and both plants thrived, however, it might be more ideal to plant a ground crop like carrots or potatoes.

 
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5. Beneficial Habitats

Provide food plants or herbs for beneficial insects such as ladybugs, wasps and hover flies by inter-planting or using borders and backdrops.

This photo shows a cover crop/companion planting of a nitrogen fixing mix. The pink flowers are from the hairy vetch. While vetch is used for nitrogen fixation, it also provides a beneficial habitat for ladybugs which prey on aphids and spider mites.


As part of a well managed IPM system, strategies employing intercropping and companion planting are utilized to increase crop diversity. In this system, many different herbs, flowers, and even weedy groundcovers are used to deter pest insects and attract beneficial predators. Insects locate their preferred food by means of sight, smell, and taste. They use sensitive receptors on their feet and mouthparts that allow them to find a certain crop from a great distance (e.g., the white cabbage butterfly can recognize the mustard oils of the broccoli family from a distance of ten miles).

Below is a partial list of plants that are useful as companion plants along with some of their attributes:

*Its important to remember that all these plants have not been tested with cannabis so prudence and care should be taken to thoughtfully plot out the appropriate planting for your garden

ANISE - A good host for predatory wasps, it also repels aphids. Deters pests from Brassicas (Cabbage, broccoli, etc) by camouflaging their odor.

BASIL - Plant with tomatoes to improve growth and flavor. Repels flies and mosquitoes

BEANS - All beans enrich the soil by fixing nitrogen. They are good for planting with all vegetables EXCEPT for Alliums (onions, garlic, leeks). Summer savory repels bean leaf beetles and will improve the beans flavor.

BEE BALM - Lures bees and hummingbirds to the garden for better pollination. Improves the growth and flavor of tomatoes.

BEETS - Good for adding minerals to the soil. Good companions are lettuce, onions and Brassicas. Do not plant with beans as they will stunt each others growth.

BORAGE - Good to plant with tomatoes, squash and strawberries. It will deter hornworm and cabbage looper. Adds trace minerals to the soil and attracts bees and ichneumon wasps. Borage will benefit almost any plant it is growing near by increasing its resistance to disease and pests.

CARAWAY - Good for loosening compacted soil so it benefits all shallow rooted crops. Attracts beneficial insects.

CATNIP/CATMINT - is one deters flea beetles, aphids, squash bugs, ants and weevils. It will also repel mice!

CHAMOMILE - Improves the flavor of cabbages, onions and cucumbers. It accumulates calcium, sulphur and potassium, returning them later to the soil. It is a host for hover flies and good wasps. Increases the production of essential oils in herbs.

CHERVIL - Improves the flavor and growth of radishes. Keeps aphids o lettuce and is said to deter snails.

CHIVES - Improves growth and flavor of carrots and tomatoes. Keeps aphids away from mums and sun flowers. When planted by roses it helps prevent black spot.

CHRYSANTHEMUM - Deters and kills root nematodes.

COMFREY - Accumulates calcium, phosphorous and potassium. A good trap plant for slugs.

CORIANDER - Repels aphids,spider mites and potato beetle. A tea made from it is a good spray for spidermite.

CUCUMBERS - Work well with sun flowers, carrots, peas and beets. Planting dill nearby attracts beneficials. Nasturtiums will improve growth and flavor. Keep sage away!

DAHLIAS - Repels nematodes

DILL - Improves the growth and health of cabbage and lettuce. Plant by tomatoes to trap the tomato hornworm. Attracts many beneficials. Do not plant by caraway or carrots!

ELDERBERRY- A decoction (the extraction by boiling water-soluble substances down) of the leaves is an effective spray for aphid and cucumber and diabroitica beetle. Repellent to moles.

GARLIC - Plant by roses to repel aphids. Deters cabbage loopers, codling moth and peach borers.

GERANIUM (Zonal) - Repels cabbage worm, corn ear worm and leaf hoppers. Plant by grapes, roses, corn and cabbage.

HYSSOP - Highly attractive to bees but do not plant near radishes.

LEMON BALM - Deters many bugs, especially mosquitoes and squash bugs.

LOVAGE - Improves the growth and flavor of most plants. Encourages beneficial predatory ground beetles.

MARIGOLD - Discourages beetles, white flies and nematodes. Acts as a trap plant for spidermites and slugs. Do not plant near cabbage or beans.

MARJORUM - Improves the growth and flavor of all vegetables.

MINT - Deters cabbage moth,ants,rodents,aphids and fleas. Attracts hover flies and predatory wasps. Attractive to earthworms.

NASTURTIUM - Plant as a barrier trap around tomatoes, radishes, cabbage, cucumbers and fruit trees. Deters white flies and squash bugs. Good trap crop for black aphid.

ONIONS - Plant with carrots, leek, beets, lettuce, Brassicas and strawberries. Improves other plants disease resistance. Do not plant with peas.

PEPPERS, HOT - Root exudates prevent root rot and Fusarium diseases of eggplant, tomatoes, swiss chard, squash and cucumbers.

ROSEMARY - Plant with cabbage, carrots, beans and sage. Deters cabbage looper and bean beetles.

TARRAGON & THYME - Both are beneficial to plants throughout the garden.

YARROW - Increases the production of other herbs essential oils. Attracts beneficials.


Pests and the Plants that Repel Them

from: Cornell Cooperative Extension

Certain plants are believed to repel insects.
Use the list below to help you map out your next planting arrangement.

Pest - Repellent Plant(s)
Ant - Mints, tansy, wormwood
Aphid - Most aromatic herbs, including catnip, chives, clover, coriander, eucalyptus, fennel, garlic, larkspur, marigold, mustard, nasturtium, peppermint, spearmint
Asparagus beetle - Basil, calendula, nasturtium, parsley, tansy, tomato
Cabbage butterfly - Southernwood, tansy
Cabbage Looper - Catnip, dill, eucalyptus, garlic, hyssop, nasturtium, onion, pennyroyal, peppermint, rosemary, sage, southernwood, spearmint, thyme, wormwood
Cabbage maggot - Garlic, marigold, radish, sage, tansy, thyme, wormwood
Carrot fly - Basil, leek, lettuce, nasturtium, onion, rosemary, sage, tansy, tobacco, wormwood
Codling moth - Garlic, wormwood
Colorado potato beetle - Catnip, coriander, eucalyptus, marigold, nasturtium, onion, tansy
Corn earworm - Cosmos, geranium, marigold, thyme
Cucumber beetle - Catnip, corn, marigold, nasturtium, radish, rue, tansy
Cutworm - Spiny amaranth, tansy
Flea beetle - Catnip, marigold, nasturtium, peppermint, rue, spearmint, southernwood, tansy, tobacco, wormwood
Flies - Basil, tansy
Imported Cabbageworm - Dill, garlic, geranium, hyssop, peppermint, nasturtium, onion, pennyroyal, sage, southernwood, tansy, thyme, borage
Japanese beetle - Catnip, chives, garlic, nasturtium, odorless marigold, tansy, white geranium
Leafhopper - Geranium, petunia
Mexican bean beetle - Garlic, marigold, nasturtium, rosemary, savories
Mouse - Wormwood
Mole - Castor bean, narcissus
Mosquito - Basil
Nematodes - Calendula, French marigold
Peach borer - Garlic
Pests in general - Oregano
Rabbit - Garlic, marigold, onion
Slug and snail - Fennel, garlic, rosemary
Spider mite - Coriander, dill
Squash bug - Catnip, marigold, nasturtium, peppermint, petunia, radish, spearmint, tansy
Squash vine borer - Radish
Tomato Hornworm - Borage, calendula, dill, opal basil, thyme
Whitefly - Basil, nasturtium, peppermint, thyme, wormwood
Wireworm - Clover

Selected References

IPM & Beneficial Insects - Insectary Plants - UCIPM

INTEGRATED PEST MANAGEMENT & COMPANION PLANTING

companion planting - Sloat Garden Center

]Companion Plants for Aphid Pest Management - MDPI