Companion planting means growing certain plants next to each other (or not, as the case may be) to naturally enhance plant growth and deter unwelcome visitors naturally. This is a great idea to avoid pesticides. You can do the same with wildlife (for instance, encouraging habitats for ladybirds will take care of aphids).
Companion Planting for Beginners is the ultimate illustrated guide to know which plants to grow alongside others. From tomatoes (to help protect carrots) or mint (that can repel slugs near lettuce), companion planting can also improve soil quality and increase yield. In this book, an organic gardener offers a chart of plant pairings for common garden vegetables, plus troubleshooting tips and advice on setting up the perfect vegetable garden.
Many companion plants are toxic to pets, so it’s important to avoid them. These include alliums (garlic, onion, leeks, chives, shallots), borage and all bulbs/marigolds. Learn how to create gardens safe for pets (use humane slug/snail deterrents).
Use no-dig gardening to protect wildlife. Use fruit protection bags (over netting, which can trap birds and wildlife). Avoid facing indoor foliage to outdoor gardens, to help stop birds flying into windows.
A few companion planting ideas:
- Plant beans alongside spinach & tomatoes
- Plant horseradish next to potatoes
- Plant pumpkins next to sunflowers
- Plant asparagus with parsley & tomatoes
- Plant runner beans near strawberries, radish & celery
- Plant turnips near broccoli & peas
- Thyme helps to deter blackfly on roses.
- Alliums (garlic, onion, shallots, chives) near carrots (to stop carrot fly). Mint can also be used (but in a pot, it can get out of control).
- Mint with brassicas (deters flea beetles from laying eggs).
- Marigolds are good to deter whitefly on tomatoes.
- Borage (taste like cucumber) improve flavour of strawberries
Avoid ‘negative companion planting’ (like planting tall and short plants next to each other, as one will block out the light). Don’t grow drought-tolerant plants next to ones that need a lot of water.
Allelopathic plants are ‘negative’ in that plants release chemicals that don’t help plants. For instance, walnut trees usually don’t grow well with other plants, nor do garlic/onions alongside peas, nor mint/onions alongside asparagus.
The Science Behind Companion Planting
Plants interact with the environment and neighbouring plants, through chemical symbols. Some release substances to deter unwelcome visitors, while others may boost growth, by improving nutrient uptake. Examples are:
- Tomatoes and Basil – Not just for your pasta sauce, basil enhances tomato flavour.
- Carrots and Onions – Onions repel carrot flies, ensuring healthier carrots.
- Corn and Beans – Beans fix nitrogen in the soil, benefiting corn’s growth.
But beware of poor pairings:
- Tomatoes and Corn – Both attract similar pests, doubling trouble.
- Carrots and Dill – Dill may stunt carrot growth if planted too closely.
Companion planting can also lead to bigger harvests (radishes break up soil to allow spinach roots to spread more easily). And also improves soil health (legumes add nitrogen to soil) and deep-root plants like comfrey bring up nutrients from the depth, to enrich surface layers).
Practical Tips for Companion Planting
Think of your garden like a puzzle. Consider each plant’s needs and how they complement others. Plant tall crops like corn to provide shade for sun-sensitive partners like lettuce. This strategic placement maximises space and benefits.
Enthusiasm is great, but don’t rush. Mixing incompatible plants can lead to poor results. Avoid overcrowding, which restricts air flow and can lead to diseases. Research pairings and give plants the space they crave.
Success Stories of Companion Planting
- The Three Sisters Garden: A classic technique from Native American agriculture, this involves corn, beans, and squash. Corn provides a trellis for beans, beans fix nitrogen, and squash shades the ground, reducing weeds.
- The Rose and Garlic Bed: In a quaint English garden, roses grew more robust and fragrant when garlic was planted nearby. Aphids stayed away, defeated by garlic’s natural repellent properties.
