Companion planting is the art of growing different plants together to achieve certain benefits, such as helping with pest control, encouraging pollination or increasing crop yields. With a little thought, companion planting can also create a feast for the eyes, turning a functional veg plot to a glorious thing of colour and beauty.
We asked The Sunday Gardener, Carol Bartlett, for her advice on companion planting. Here are some of her top tips…
What is companion planting?
Companion planting has long historical roots, harking back to a time when there were no chemicals to control pests or to feed plants, and gardeners relied purely on nature. In the 1970s, when organic gardening became popular once again, companion planting enjoyed a renaissance which continues to this day.
But there’s another aspect to companion planting which is equally popular: using contrasting plants and vegetables to create an aesthetically appealing kitchen garden. This style of planting is illustrated above, in this RHS garden at Harlow Carr where the veg plot looks immaculate and is full of colour. In and amongst the vegetables are sweet peas, nasturtiums, tagetes and lavender, creating a veg plot that’s both beautiful and productive.
It’s fair to say that recent studies have been less than conclusive about the direct benefits of companion planting. I view it as a way to deter pests while also making my vegetable plot more attractive. In this wider context, which includes the aesthetic look of the veg plot, perhaps it’s less important to measure the direct benefits scientifically.
How companion planting works: repel and sacrifice
There are two types of companion plants: some are grown because their smell repels unwanted insects, and others are grown as a sacrifice to keep the main crop insect-free.
One of the best known combinations recently receiving tentative scientific approval is planting tomatoes together with French Marigold (Tagetes patula) to reduce whitefly. Marigolds contain a substance called limonene, and scientific data confirms that tomatoes grown alongside limonene suffer less from whitefly. It’s also true that tomatoes and tagetes make a colourful planting combination!
Another good companion for tomato plants is basil. They look and taste good together, and this scented herb is said to repel pests.
Plagued by aphids? Nasturtiums make good aphid traps. The flowers secrete mustard oil which lures the insects away from brassicas and other crops. In a similar vein, some people use French marigolds as slug bait – meaning they’re used as sacrifice plants to keep your lettuce free from slugs.
Strong smelling plants, such as lavender, mint and sage are reputed to confuse and repel aphids and other unwanted insects away from many vegetables, including carrots. The combination of alliums and carrots is often recommended, but given the tenacity of the carrot fly, I personally always use a physical barrier as well. I’m happy to plant alliums and chives around my carrots, but put my faith in a sturdy barrier!
Companion planting to attract pollinators
We’re becoming ever more aware of the vital role of pollinators and bees to our food culture. Carefully chosen companion plants definitely help to attract pollinators to your vegetable plot, and the more pollination, the better the yield.
The English pot marigold, Calendula, is so easy to cultivate that it almost grows itself. Unlike the French marigold it’s of no interest to slugs, who ignore it, but pollinators like hoverflies, lacewings and ladybirds are incredibly attracted to its lovely zingy yellows and oranges. What’s more, Calendula will seed itself from year to year with no gardening attention whatsoever.
Want to increase your tomato yields? Encourage more bumble bees. In fact, bees are so essential to tomatoes that boxes of them are often imported into commercial greenhouses to work their pollinating magic. In your own greenhouse, chives are one of the best ways to attract bees and are ideal planted with tomatoes. A few pots of chives near the entrance and around your plants will welcome them in!
Another herb that’s a great friend of pollinators is borage, with its lovely delicate flowers that attract bees, butterflies, and hoverflies. But if I could grow just one plant to attract pollinators it would be oregano, beloved of all pollinating insects.
For more information about companion planting combinations, see the chart in our Companion Planting Guide. Know of any combinations we haven’t mentioned? Please leave us a comment and share your tips.
Carol Bartlett, The Sunday Gardener, lives in the north of England where she has created a diverse garden including wildflowers, natural areas, herbaceous borders, a wildlife pond, trees and wetland plants, along with a vegetable plot. She has been gardening, reading, researching and photographing plants for over twenty years and her website is a popular resource for gardeners young and old.