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Companion Planting Deters Insects, Mice, Rabbits, and Moles

Basil and tomatoes. Carrots and onions. Mosquito fern and rice. Squash, maize, and beans. Marigolds and tomatoes. All of these are examples of companion planting, also known as polyculture, plant associations, or intercropping. Some of these combinations are said to deter unwanted insects, along with mice, moles, and other rodents.

basil and tomatoes companion planting
Basil grows well aside tomatoes and repels many pest insects.

Is companion planting folk wisdom or based in science?

You hear a lot about companion planting once you start reading about organic gardening. But is there any truth to it? The answer is yes, depending on what you’re trying to achieve.

Folk wisdom holds that companion planting improves the flavor of some plants. Since the flavor of the plant is influenced by literally hundreds of factors, including soil, weather, variety, and the time of day it’s picked, we won’t go there. But companion planting has proven its worth time and again in shading and supporting plants, improving soil, attracting beneficial insects, improving pollination, fixing nitrogen in the soil, and repelling insect pests and some mammals like mice.

Diverse plantings will attract and retain beneficial insects, including the predator and parasitoid species so important for IPM (Integrated Pest Management) and PHC (Plant Health Care) strategies. Furthermore, the presence of several species in a given area disrupts the ability of many herbivorous insects to discover their appropriate host plants for feeding or egg-laying, apparently through both visual and olfactory miscues.
The theory suggests that time wasted on non-host plants reduces reproductive efficiency of specialist insects, as they consume metabolic resources on aborted host selection events.Linda Chalker-Scott, University of Washington
companion planting
Dill, Bachelors Buttons, and wildflowers planted near my raised garden beds deter unwanted insects and attract pollinators.

Planting annuals like Marigolds, Zinnias, Sunflowers, Sweet Alyssum, Borage, and Cosmos in your vegetable beds attract pollinators all season. As the pollinators are close by your vegetables and fruits when they’re in flower, pollination increases on those food crops and, consequently, their yields. Additionally, many flowering plants are known to repel certain insect pests: Ants won’t go near mints, flea beetles hate Marigolds, and flies and mosquitos are repelled by Basil.

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You can also use companion planting to attract birds that eat unwanted insects. For instance, sunflowers planted in or near your vegetable beds serve as an excellent perch for small birds. From that spot, they can spy insects in the garden which become a fast meal.

Reasons for Companion Planting

  • Shade: Large plants provide shade for smaller plants. For instance, squash shades corn roots and tomatoes; peppers or corn shade leafy greens.
  • Natural support: Tall plants provide a structure for vining plants to climb – pole beans and corn are a great example. The thick stalks of sunflowers can also support cucumbers or peas.
  • Weed Suppression: Planting crops with dense foliage like squash suppresses weeds around upright plants like sweet corn. Clover suppresses weeds anywhere.
  • Insect and pest control: Many plants can be used to repel insects and mammal pests like rabbits.
  • Attract beneficial insects: Carrots, dill, parsley, and parsnip attract praying mantises, ladybugs, and spiders – beneficial insects that keep pest insects under control. Beneficial insects also help increase pollination of fruits and vegetables.

Ultimately, you’ll have to experiment in your garden to find the best companion plants, as much will depend on the vegetables and fruit you grow, the amount of garden space you have, and which pests seem to return each year.

companion planting pollination
A bee attracted to basil flowers helps pollinate the entire garden.

The best use of the chart below is as a preventative. For instance, plant companions like Dill, Marigolds, and Onions in your cabbage beds every season from the start to keep pests at bay like Cabbage Moths, Cabbage Loopers, and Cabbage Butterflies. Plant leafy greens near tall plants and take advantage of the shade they cast. Plant beans at the base of corn – beans fix nitrogen which the corn needs and the corn provides a sturdy structure for the beans to climb. Companion planting has many benefits.

Companion Plants that Repel Insect and Mammals Pests

Source: University of Rhode Island (https://web.uri.edu/mastergardener/files/J4-Companion-Planting-Pests-and-Plants-That-Repel-Them.pdf) and various. Note that Tansy is considered invasive in some areas.
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Insect or Mammal PestRepellent Plants
AntsCatnip, Chrysanthemums, Mints, Mugwort, Sagebrush, Spearmint, Tansy, Wormwood
AphidsCatnip, Chives, Clover, Coriander, Dill, Eucalyptus, Fennel, Garlic, Larkspur, Marigold, Mustard, Nasturtium, Peppermint, Petunias, Spearmint
Asparagus BeetlesBasil, Calendula, Nasturtium, Parsley, Petunia, Spearmint, Tansy, Tomato
Cabbage ButterfliesDill, Geranium, Hyssop, Southernwood, Tansy
Cabbage LoopersCatnip, Dill, Eucalyptus, Garlic, Hyssop, Mugwort, Nasturtium, Onion, Pennyroyal, Peppermint, Rosemary, Sage, Sagebrush, Southernwood, Spearmint, Thyme, Wormwood
Cabbage MaggotsGarlic, Marigold, Mugwort, Radish, Sage, Sagebrush, Tansy, Thyme, Wormwood
Cabbage MothsSage, Lavender, Onion, Peppermint, Tansy
Cabbage WormsBorage
Carrot FliesBasil, Chives, Leek, Lettuce, Mugwort, Nasturtium, Onion, Rosemary, Sage, Sagebrush, Tansy, Tobacco, Wormwood
Codling MothGarlic, Lavender, Mugwort, Sagebrush, Wormwood
Colorado Potato BeetleCatnip, Coriander, Eucalyptus, Marigold, Nasturtium, Onion, Tansy
Corn EarwormCosmos, Geranium, Marigold, Thyme
Cucumber BeetleCatnip, Corn, Marigold, Nasturtium, Radish, Rue, Spearmint, Tansy
CutwormSpiny Amaranth, Tansy
Flea BeetleCatnip, Marigold, Mugwort, Nasturtium, Peppermint, Rue, Sagebrush, Spearmint, Southernwood, Tansy, Tobacco, Wormwood
FliesBasil, Tansy
HornwormBorage
Imported CabbagewormDill, Garlic, Geranium, Hyssop, Peppermint, Nasturtium, Onion, Pennyroyal, Sage, Southernwood, Tansy, Thyme, Borage
Japanese BeetleCatnip, Chives, Chrysanthemums, Four O' Clocks, Garlic, Nasturtium, Odorless Marigold, Tansy, White Geranium, Four O' Clocks
LeafhopperGeranium, Petunia
Mexican Bean BeetleGarlic, Marigold, Nasturtium, Rosemary, Savories
MouseWormwood
MoleCastor Bean, Narcissus
MosquitoBasil, Fever Tea, Lantana, Lavender, Lemon Balm, Lemongrass, Lemon Thyme, Lime Basil, Rosemary
NematodesCalendula, Chrysanthemums, French Marigold, Dahlias, Chrysanthemums
Peach BorerGarlic
Most pestsOregano, Lavender
RabbitGarlic, Marigold, Onion
Root MaggotGarlic
Slug and SnailFennel, Garlic, Rosemary
Spider MiteCoriander, Dill
Squash BugCatnip, Dill, Marigold, Nasturtium, Peppermint, Petunia, Radish, Spearmint, Tansy
Squash Vine BorerRadish
Tomato HornwormBasil, Borage, Calendula, Dill, Petunias, Thyme
WhiteflyBasil, French Marigold, Mugwort, Nasturtium, Peppermint, Sagebrush, Thyme, Wormwood
WirewormClover
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