Companion Planting For A Healthy Vegetable Patch

Why Companion Planting Earns Its Keep

Walk down any allotment site in July and you will see it happening: rows of carrots threaded through with onions, nasturtiums tumbling over the edge of a bean wigwam, pot marigolds tucked between the tomatoes. This is not just pretty planting. Companion planting is a way of working with the garden rather than against it, using scent, shade and shelter to keep pests guessing and beneficial insects well fed. On a small plot — a back garden, a half plot, three raised beds — it also makes every square foot work harder. The trick is being honest about which pairings genuinely earn their place and which are old wives' tales. The ones below do the job, season after season.

Pairings That Genuinely Work

Start with the classics, because they have survived for a reason.

• Carrots and onions. Onion and leek foliage masks the scent of carrot leaves, so carrot root fly struggles to find the crop, while carrots confuse onion fly looking for its host. Alternate rows, or sow a thin line of spring onions between each row of carrots. Thin your carrots in the evening, when the fly is less active, and water the row afterwards to settle the smell of disturbed soil.
• Beans and nasturtiums. Blackfly adore broad beans and runner beans — and they adore nasturtiums more. Sow a few plants at the end of each row as a sacrifice, then check them daily and squash the first colonies before they build. The flowers are edible and peppery, and cabbage white butterflies will lay on nasturtium leaves rather than on your brassicas.
• Brassicas and aromatic herbs. Rosemary, sage, thyme and hyssop planted close by seem to unsettle cabbage white and flea beetle. Let dill and pot marigold flower nearby to bring in hoverflies and parasitic wasps, which quietly tidy up caterpillars for you.
• Tomatoes and French marigolds. Marigold roots release compounds that suppress soil nematodes, and the flowers draw in pollinators when the tomatoes are setting fruit.
• Lettuce and radish. Radishes mark the row, break the soil crust for the lettuce and are pulled before the lettuce needs the space.
• Sweetcorn, climbing beans and squash. The famous Three Sisters works in the UK if you start the corn and squash under cover in May — the beans climb the stems, and the squash foliage shades out weeds and holds moisture.

Frost-Tolerant Crops For The Shoulder Seasons

Cold is rarely the problem; wet feet and a sudden thaw are. Choose hardy varieties and you can eat from the plot almost every week of the year. Kale, cavolo nero, winter chard and purple sprouting broccoli shrug off hard frost, and parsnips actually sweeten after a good cold snap — leave them in the ground and lift as needed. Lamb's lettuce, land cress and winter purslane will crop right through until March. Sow broad beans such as Aquadulce Claudia in late October for an early June pick, and plant garlic cloves in November for bulbs that split properly. Winter lettuce and chervil are happy in a cold frame or under a cloche, and a double layer of fleece will see most salads through a sharp night. The secret is to sow in late summer, not to try to rescue things in December.

Making Room In A Small Plot

Intercropping is where companion planting pays you back in harvest rather than in principle. Use quick crops as catch crops between slower ones: radish and rocket between brassicas, salad leaves between courgettes before the foliage fills out. Plant tall crops on the north side so they do not shade the beds, and use the edges — a row of herbs along the path, nasturtiums trailing over a wall, marigolds in the gaps where you lifted early potatoes. Sow in succession every three weeks rather than all at once, and you will avoid the glut-and-famine cycle that leaves a whole bed empty by August.

Encouraging Native Wildlife

A healthy patch is a busy one. Native plants do more for our insects than any exotic, so leave space for foxgloves, wild marjoram, yarrow and field scabious. Let chives, thyme and mint flower; the bees will thank you, and so will the hoverflies whose larvae eat aphids. A small log pile in a shady corner gives ground beetles and slow worms somewhere to live, and ground beetles are voracious slug predators. A shallow dish of water with a few stones in it helps frogs, toads and thirsty hedgehogs. Leave a gap under the fence so hedgehogs can move between gardens, avoid slug pellets entirely, and resist the urge to tidy every seedhead in autumn — goldfinches and sparrows will feed on them through the winter.

A Year Of Seasonal Care

In spring, harden off seedlings gradually, mulch with garden compost and watch for the first aphids on the soft growth. In summer, water deeply twice a week rather than little and often, and sow winter salads and kale from July. In autumn, clear spent crops, sow a green manure such as field beans on empty beds, and plant garlic and overwintering onions. In winter, keep feeding the birds, check stored crops for rot, and plan next year's rotation so no family of vegetables follows itself. Do that, and the patch looks after itself far more than you would expect.