Maximising crop yields is often a priority for vegetable gardeners – and pests such as blackfly and greenfly can present a real challenge.
But instead of turning to chemical sprays to keep pests at bay, many organic gardeners practise companion planting – growing certain plants together to boost plant health and deter pests. It can improve harvests while maintaining a balanced, healthy ecosystem.
Pesticides and weedkillers are poisons that cause harm not just to pests, but to all insects – as well as to other animals that rely on insects as a food source.
Pesticides and weedkillers also contaminate the soil, and leach into rivers and other waterways, harming aquatic life.
Working with nature – rather than against it – to grow healthy plants without the use of toxic chemicals is what companion planting is all about.
Making space for some flowers within the kitchen garden can create a magnet for beneficial insects – and can help to increase harvests.
Bees, bumblebees, butterflies, hoverflies and moths are all important for pollinating many edible crops. And some fruit and veg – such as tomatoes, strawberries and apples – are particularly reliant on our six-legged friends.
Bees and bumblebees in particular are vital to our wellbeing. More than a third of our diet is directly dependent on bees: they pollinate fruit, vegetables and cereals.
Insect populations have crashed in the last few decades, so creating habitats that help them in gardens, allotments and community green spaces is vital.
To attract these beneficial insects to your plot – and to help them with a source of food – grow nectar-rich blooms that pollinators love. Try sowing a few annual seeds amongst your vegetable plants: grow sweet peas next to beans to attract bumblebees, or sow poached egg plant here and there – hoverflies, in particular, love the cheerful yellow blooms. Cosmos, sunflowers, and single-flowered dahlias (not the frilly kind, as insects find it hard to negotiate all the complicated petals to reach the nectar) also work well.
Herbs are brilliant for attracting insects, and look quite at home in a potager-style garden. Bees love borage, which has edible flowers that look great in a salad. Rosemary, thyme and lavender also attract a range of pollinators – and the strong scent of these plants can deter pests such as aphids.
Butterflies and moths
When we think of pollinating insects it’s often bees that spring to mind – but butterflies and moths are effective pollinators too.
Sadly, British butterflies are among the most threatened in Europe – 80% of our butterflies have declined since the 1970s, according to Butterfly Conservation (www.butterfly-conservation.org).
Climate change is having a big impact on these insects – especially those found in northerly locations, where warmer temperatures are affecting species that are adapted to cooler or damper climates.
Growing plants to feed butterflies and moths (and their caterpillars) can help. Easy-to-grow herbs, such as rosemary and marjoram, attract butterflies – or try cornflowers, globe thistles, lavender or verbena bonariensis.
To attract moths, grow night-scented plants like honeysuckle, jasmine, nicotiana and night-scented stock.
It’s also important to provide a source of food for the caterpillars of butterflies and moths. Leaving a small patch of garden or the allotment to go wild can really help. The sorts of plants that grow in wild areas – docks, dandelions, nettles and thistles, for example – are excellent sources of food for butterfly and moth larvae.
Hoverflies, lacewings and ladybirds
Attracting certain insects can help with pest control, as well as pollination.
For example, the larvae of hoverflies feed on aphids. Hoverflies like French marigolds. So by planting a few marigolds around your tomatoes, you can attract hoverflies and help to protect your crop. The scent of French marigolds repels whitefly too, giving your tomatoes another line of defence.
Lacewings and ladybirds eat pests too – grow yarrow, dill or coriander to encourage them to visit your plot. Create shelter for ladybirds and lacewings with some logs or branches piled into a corner – and avoid cutting down dead stems in winter, as these often harbour hibernating insects.
As well as attracting beneficial insects to your plot, some flowers and plants will keep pests at bay. Calendula, for example, is said to repel whitefly from tomatoes, and can lure aphids away from beans.
Planting certain vegetables alongside each other can also deter pests. Chives, onions or leeks planted alongside carrots can help to prevent carrot fly attacks – and in return, the scent of carrots repels onion fly and leek moth. And by planting strong-scented mint and coriander near your tomatoes you can keep aphids and whitefly away.
You could also try growing a ‘sacrificial’ crop such as nasturtiums. Cabbage white butterflies like to lay their eggs on brassica plants – but they’re quite fond of nasturtiums too. So planting nasturtiums near cabbages may distract the butterflies, and keep them off the crop.
Does it work?
As with many garden practices, some people are sceptical about companion planting – whilst others swear it’s key to a bumper harvest.
Using companion planting alongside other methods – for example, crop rotation and physical barriers such as insect netting – can help keep your plants healthy and pest-free without having to rely on chemical alternatives.
The level of success you have will depend on the conditions in your garden. In our garden, for example, carrot fly is a particular problem, and we’ve never had much luck growing carrots – even inter-planting with spring onions doesn’t keep the pests away.
But last year, we grew lots of flowers – cosmos, single-flowered dahlias, sunflowers and calendula – in amongst the veggies. We had some pretty good results, with French beans, courgettes and butternut squash all growing in abundance.
In fact, we’ve never had any success with butternut squash before. Was it because of the flowers? Maybe. But one thing that’s certain is that the veggie patch looked beautiful – and we had vases of freshly cut homegrown flowers on our windowsills all summer!
So why not try it, and see what happens in your own garden? Even if companion planting doesn’t increase your crop yield, you’ll be helping our struggling pollinators by providing a much-needed source of food – and, with all those colourful blooms, your vegetable patch will look lovely!