Make your garden do double duty with matchmaking

Some things are famed for going well together. According to the song these include love and marriage, a horse and carriage, and we could add gin and tonic in there too.

You might not have considered it, but it’s a philosophy that can easily be extended to the garden. Perhaps you already have a standing agreement in place along the lines of “I’ll cut the grass if you do the weeding,” but partnership working can include plants too. This is the topic of a new book by horticulturalist Josie Jeffery. Good Companions (£9.99, Ivy Press) bills itself as a “mix and match guide to companion planting” and it makes what can be a complicated topic a lot easier to understand.

“Companion planting is a way of working with nature instead of against her to create a more sustainable garden, as well as it being more environmentally friendly and cheaper,” says Jeffery. “You can cut out the use of chemicals which degrade your soil by using plants to make natural pesticides, herbicides and fertilisers.” She believes that companion planting can help reduce the manual work that is involved in the day-to-day business of caring for a garden. A green mulch, for instance, can help reduce the need for weeding and watering by suppressing weeds and helping to prevent water evaporation from the soil.

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Most gardeners are aware that planting flowers can attract pollinating insects and that some herbs will keep aphids away, but few of us have a detailed knowledge of the specifics. Good Companions guides us through this method of gardening, looking at history and botany as well as giving hands-on advice. “Planting at close proximity allows each plant to benefit each other’s growth such as providing shade and shelter or releasing nutrients into the soil, making it richer for their neighbouring plants,” says Jeffery. “Some plants act like a vegetative plough and turn the soil with their roots, breaking it up for plants that prefer looser soil.”

Nature has its own pesticides – species that are known to deter pests such as aphids, attract pollinators and release toxins through their roots. These toxins remain in the soil for more than a year and kill pest nematodes that can destroy the root system on host plants. Marigold (Calendula officinalis) is one of the most popular companion plants to grow for these reasons. Then there is trap cropping: one plant acts as a “trap” to lure away pests from the main crop. Nasturtiums can be used in this way to keep aphids from roses and lettuces. If you’re looking for plants that produce nectar and pollen to attract pollinators such as bees, butterflies and hoverflies then fennel, sunflower and lemon balm all fit the bill. And did you know that some herbs can improve the flavour of neighbouring plants? Interplanting basil with tomatoes is a great way to test the theory.

Jeffery says that she is a big fan of growing flowers in the vegetable garden. “Flowers can do two jobs at once: they can attract insects with their beautiful colours and scents as well as be attractive for their human spectators,” she says. If you are going to plant flowers with vegetables then it’s important to choose single flower types rather than double varieties (which tend to be hybridized and offer little or no food to pollinators). Having a range of flower shapes will attract a wider range of insects and if you can keep your blooms going over a long period, all the better. Other tips for the vegetable patch include intercropping onions and leeks with carrots to mask the scent of the carrots and confuse carrot flies; and if you want to help out nitrogen-hungry crops, such as cabbage, intercrop them with clover.

Good Companions contains some fascinating accounts of companion planting around the world. In China, for example, the best known match is the aquatic plant mosquito fern (Azolla caroliniana) with rice crops. Jeffery explains that Azolla also efficiently blocks out light to prevent any other plant competition and is a “bio-fertilizer”, meaning it captures atmospheric nitrogen and makes it available for the rice. The Azolla also provides a nutritious fodder for livestock, and controls the mosquito population by reducing the oxygen levels in the water where mosquitoes lay their eggs. Jeffery says she enjoyed researching systems used around the world: “The most obvious example is the ‘three sisters’ planting method where beans, squash and sweetcorn are grown together,” she says. “But I particularly enjoyed uncovering the ‘push pull’ cropping system by Rothamsted research. Their method uses companion planting to attract the stem borer pest to another ‘trap crop’ by ‘pulling’ it away from the main crop as well as ‘pushing’ them away with a repellant plant. What thrills me is how it this simple method has helped save livelihoods in Africa.”

The Good Companions directory section has been carefully thought out to make it easy to navigate. The pages are divided into three strips and the central one represents the crop you’ve already got or have decided to plant. You then flip through the colour-coded top and bottom strips to find the perfect partners. Plants listed on the top strip support above-ground needs, such as attracting beneficial insects. The bottom strip features companions that support below ground needs, like providing vital soil nutrients. It’s a time-saving feature that makes getting started with companion planting a lot less daunting.

Jeffery says that she has plenty of favourite combinations, particularly those that protect her precious fruit and vegetables. “My favourite fruit is strawberries, so that combination would be chives and strawberries,” she says. “And for vegetables it would be the good old potato which can be accompanied by calendula, and if you make a bed of comfrey leaves in the bottom of your potato trenches before planting they provide a good nutrient boost for your sacred spuds.” So if you want to try a friendlier approach to gardening, Good Companions has all the equipment to start you off on the right foot.

Good Companions: The Mix & Match Guide to Companion Planting by Josie Jeffery (£9.99, Ivy Press) is out now.