Whether you have a large yard or just a few pots on a balcony, companion planting is an age-old and clever technique for achieving a productive and healthy garden. By thoughtfully pairing your crops, you create an ecosystem where plants help each other out. This strategy is particularly rewarding for container gardening or in small spaces, where every square inch counts!
What is companion planting?
Companion planting, also known as intercropping, involves growing plants side-by-side that have beneficial effects on one another. These positive interactions can take many forms: some plants repel harmful insects, others attract precious pollinators, improve soil fertility, or even help their neighbours better resist diseases. Conversely, some plants can negatively affect each other, so it's best to keep them apart.
The many benefits of companion planting
Adopting companion planting in your garden offers a wide array of advantages:
- Attract pollinators and beneficial insects: Flowers like borage, calendula, nasturtium, or chives in bloom attract bees, butterflies, and other pollinators essential for the fruiting of your vegetables (zucchini, tomatoes, cucumbers, etc.). Some also attract beneficial insects, like hoverflies (whose larvae devour aphids).
- Deter harmful insects: This is one of the major benefits! Certain aromatic plants are true natural repellents:
- Basil planted near tomatoes can help repel aphids and whiteflies.
- Marigold (Tagetes spp.) is known for repelling soil nematodes (microscopic worms that attack roots) and some other pests like whiteflies.
- Peppermint (be careful, it's invasive; grow it in a pot!) can repel aphids and cabbage white butterflies.
- Dill can protect cabbages by attracting parasitic wasps that prey on caterpillars.
- Promote growth and soil health: Plants from the legume family (peas, beans, lentils, clover) have the unique ability to fix nitrogen from the air into the soil, thanks to bacteria on their roots. This nitrogen then becomes available to neighbouring plants, which need it for their growth.
- Help prevent diseases: Some plants have antifungal and antibacterial properties. For example, garlic and onion planted near other crops can help reduce the incidence of certain fungal diseases.
Practical guide to companion planting in the vegetable garden
Here are a few examples to get you started:
Winning duos (and trios):
- Tomatoes and Basil: A classic! Basil is said to repel certain tomato pests, and some gardeners claim it even improves the taste of tomatoes. Marigolds are also good companions for tomatoes.
- Carrots and Onions (or leeks, chives): The smell of onions and their relatives confuses the carrot fly, while carrots can deter the leek moth. A great example of mutual protection!
- Strawberry plants and Basil or Borage: Basil can help keep away aphids and slugs. Borage, in addition to attracting pollinators, is said to enrich the soil and stimulate the growth of strawberry plants.
- Cabbages and Aromatic Herbs (Dill, Rosemary, Sage, Mint): Many aromatic herbs can help protect cabbages from their specific pests, like the cabbage white butterfly. Dill is particularly recommended.
- Cucumbers and Dill or Nasturtium: Dill attracts pollinators. Nasturtiums can serve as a trap crop for aphids, luring them away from your cucumbers.
- Beans and Potatoes: Beans (especially bush beans) fix nitrogen, which can benefit nutrient-hungry potatoes. Additionally, beans may help repel the Colorado potato beetle.
- The "Three Sisters" (Corn, Climbing Beans, Squash): This traditional Indigenous American planting method is a model of ingenuity. Corn acts as a trellis for the climbing beans. The beans fix nitrogen, benefiting all three. The squash, with its sprawling leaves, covers the ground, limiting weeds and conserving moisture.
Combinations to avoid:
It's just as important to know which plants don't get along well:
- Tomatoes/Eggplants/Peppers and Potatoes: All these plants belong to the Solanaceae (nightshade) family. Growing them together significantly increases the risk of spreading common diseases (like blight or early blight) and pests.
- Cabbages and Strawberry plants: Cabbages can attract white grubs, which may damage the roots of strawberry plants.
- Fennel and most vegetables: Fennel has a negative allelopathic effect on many plants (it releases substances that inhibit their growth). It's best to grow it separately.
- Peas or Beans and Alliums (garlic, onion, leek, chives): Plants from the garlic family can hinder the growth of legumes.
- Corn and Tomatoes: They are both susceptible to common pests like the corn earworm (which is also the tomato fruitworm).
Companion planting specifically in pots and containers:
The art of companion planting is even more relevant when space is limited:
- In a large pot, pair a tomato plant with basil at its base.
- Plant chives or parsley at the base of your potted roses to help deter aphids.
- A trailing nasturtium on the edge of a vegetable container (like peppers or eggplants) can attract aphids to itself, diverting them from your main crops.
- Strawberry plants in a planter box do well with a few lettuce or spinach plants, which have different root systems and don't compete directly.
Companion Planting Chart
To guide you, here is a more comprehensive chart to help you find the perfect companion.
Click on the image to view a PDF file.
Note: This chart is a summary. Interactions can sometimes vary depending on varieties and growing conditions.
Tips for successful companion planting
- Observe carefully: Companion planting isn't an exact science. What works wonderfully in one garden might be less effective in another. Take note of what works well for you.
- Don't neglect basic needs: Companion planting doesn't replace good gardening practices. Ensure all plants receive enough sunlight, water, and nutrients.
- Integrate with crop rotation: Companion planting is a powerful tool, but it's even more effective when combined with good crop rotation from one year to the next to prevent soil depletion and the establishment of pests and diseases.
- Consider density: Don't overcrowd your plants, even if they are good companions. Good air circulation is essential for preventing diseases.
Companion planting is an ecological and smart approach to gardening. By choosing the right combinations, you'll promote biodiversity, reduce the need for pesticides, and enjoy more abundant harvests and healthier plants. So, give it a try, experiment, and rediscover the joy of collaborating with nature!
