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Protect your crops with plant partners

We all want to be picking plenty of veg from our allotments, borders and containers – but there are ways to maximise the chances of a better harvest.

Companion planting works on the premise that planting certain things together will free one or the other plant from pests, or boost productivity. Scent and sacrifice play a big part in this equation. The strong scent of one plant can help prevent pests homing in on another which you consider more valuable.Protect your crops with plant partners

What you plant with your crops can have a significant impact on your harvest. So, how can we reap the richest rewards?

French and runner beans: Grow sweet peas to climb up wigwams and other stakes among your bean plants and you should do well. Pollinating insects will be attracted to the sweet pea flowers and are then likely to pollinate your beans, plus they’ll make the area look prettier.

Cabbages: Mix your cabbages with French bean plants, nasturtiums or Shungiku, the edible chrysanthemum, which can reduce attacks by caterpillars.

Greenhouse companions: French marigolds (Tagetes patula) deter whitefly from visiting your greenhouse. Plant a few under tomatoes to keep them at bay. Plant basil next to tomatoes to keep the aphids off, although they will go for the basil. Nicotiana will attract whitefly, keeping them off other plants.

Herbs and nettles: Almost all aromatic herbs are generally beneficial, as their smells confuse pests. Chamomile is thought to be good for healing sick plants. Nettles are reckoned to be good for neighbouring plants and increase the volatile oils in such plants as valerian, mint, sage and rosemary, so the potency of many plants increases measurably when planted near nettles. Summer savory, a strong herb, has been planted next to broad beans to protect them from black bean aphids.

Hyssop: Plant strong-scented hyssop among brassicas to ward off cabbage white butterflies. Artemisia is also effective for this, preferably in a sheltered spot so the wind doesn’t carry the strong smell away.

Mint: If you have an ant infestation in your greenhouse, tear off a bunch of mint and place it where the ants are congregating. They should disappear fast, but replace the bunches of mint every couple of days to ensure they don’t return.

Use tall plants such as sweetcorn or peas to provide shade for crops that are prone to bolting, such as lettuce, coriander and spinach.

Leeks: Pungent crops such as leeks, garlic and chives can confuse insects including carrot flies, onion flies and leek moths, so plant them with carrots if you want to stop carrot fly ruining your crops. When leeks and carrots are planted together, their scents act as repellents for each other’s pests.

Nasturtiums: These pretty annuals secrete a mustard oil that insects love. Use them as a sacrificial crop to save your brassicas, while in the greenhouse they’ll protect your tomatoes and cucumbers from whitefly.

Pot marigolds: You can reap much greater harvests by planting annuals which are attractive to pollinating insects close to your fruiting vegetables such as courgettes, beans and tomatoes. Sow them in autumn to overwinter and they should flower in time to attract insects in early summer, which will boost your harvest.

Radishes: These fast-growing roots can be grown effectively with carrots. Plant them at the same time and the radish seeds will germinate ahead of the carrot seeds, loosening the soil for the germinating carrots. When you harvest the radishes a few weeks later, the carrots will still be young but will then have more space to grow.

Plant garlic among roses to ward off aphids

Best of the bunch – Penstemon

These pretty perennials produce elegant spires of foxglove-type flowers in a range of warm reds, pinks, purples, blues and whites, providing a riot of colour to your borders in summer. They have a reputation for being tender, but should come back in subsequent years in all but the coldest regions. Plant them in full sun or light shade in any fertile, moist, free-draining soil. Keep them well-watered in dry spells and deadhead regularly to keep the plants healthy. In autumn, limit windrock and tidy up borders by cutting back penstemon by about a third, being sure to leave enough foliage to provide winter protection. To ensure a good show in subsequent years, feed them in spring with a general-purpose fertiliser and add well-rotted organic matter. Trim them once the hard, winter weather is over (usually in late April or early May). Until then, old stems provide valuable frost protection for the new shoots.

Good enough to eat – French beans

French beans range from dwarf to tall, with pods that can be eaten whole or sliced, or shelled for their seeds, either fresh (flageolets) or for drying (haricot beans). They can be sown in pots or under glass in spring, then planted out after the last frosts. If you plant successional sowings the harvest can last for six to eight weeks. Earth up stems and support dwarf types with twiggy sticks to stop them from getting splashed by soil. If you are growing haricot beans, leave the pods on the plant until brown, hang up complete plants to dry then shell out the seeds for storing. When pods start to form in July, pick them regularly because if seeds start to mature in unpicked pods, flowering will stop. Good varieties include ‘Masterpiece Stringless’ and ‘Purple Queen’. Dwarf French beans don’t need insects to pollinate the flowers, making them an ideal early or late crop under glass.

What to do this week

If you want your hydrangeas to remain blue next season, water regularly with a solution of colourant available from garden centres

Finish splitting congested clumps of bearded iris

Spread a fresh mulch of compost around heathers

Propagate tender perennials from cuttings, including fuchsia, osteospermum and argyranthemums

Feed hanging baskets and containers every week to boost blooms

Keep an eye out for rose suckers growing on rootstocks from below ground level, dig the soil to find the point of origin and pull cleanly away

Pick lettuce while young and tender, cutting alternate plants to allow others more space to develop

Trim off the foliage of strawberry plants to just above the crowns after fruiting, removing unwanted runners

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Remove blanket weed from ponds by pushing a cane into the water and twisting it out

Re-apply shading paint in the greenhouse to reduce high temperatures


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