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Companion planting is a tradition rather than an exact science, but it is rooted in centuries of knowledge and growing experience. Essentially, it's about growing the right plants together to benefit each other mutually, becoming strong, healthy and productive. But how does this work?

Matchmaking plants can help to fend off predators and disease, improve flavour and flower-power by encouraging healthy root systems, and even conserve water. It's an organic method of growing that has been practised across many different cultures around the world and is all about working in tandem with the powers of nature and creating a healthy ecosystem in your garden.

It makes sense really – grow a big plot with rows and rows of the same plant and you risk losing them all if an infestation of blackfly, blight or some other disease affects just one plant, as it will tear through them all. By mixing up the planting you can help to manage the spread of disease and distract undesirable insects.

However, it's not just about keeping the bad stuff at bay. Companion planting is as much about encouraging good, strong and fruitful growth. For example, plants in the legume family – beans and peas – help to enrich the soil for their neighbours. Their roots produce a natural store of nitrogen via nodules on their roots that all plants need for healthy growth.

Some of the key features of common companion plants are colour and scent. These help to attract beneficial insects and pollinators and distract and confuse the unwanted insects. For example, sunshine-flowered calendulas (marigolds) attract hoverflies, which are keen pollinators, as well as ladybirds and lacewings which feed on aphids and put off whitefly which can damage young shoots. So, as well as being attractive to look at and good to use in foods, teas and tinctures, they have many benefits to their fellow plants.

Companion planting works for flowering plants as well as food crops – roses can be prone to aphids, blackfly and greenfly and a bed of roses underplanted with thyme will have a good chance of fending off infestations, as the scented thyme will deter pests and the flowers will attract hoverflies and other beneficial insects to prey on them.

However, if you are growing food, it's a great way to promote healthy crops organically. One of the classic companion combinations is known as the Three Sisters growing method and originates from the agricultural techniques used by native Indian tribes in the plains and prairies of North America. By growing sweetcorn, climbing beans and squash together, you create a family of plants that won't compete with each other but, as a unit, will be more productive. The principle works on the basis that the sweetcorn provides strong upright stems that are natural supports for the beans to climb up; the beans provide the nitrogen-fixing nodules in their roots that feed the soil and the lush leaves of the squash shade the roots, helping to conserve water and control weeds.

Many culinary herbs are good companion plants. Strongly scented leaves and flowers of plants like lavender and sage are a natural repellent for many insects. They dislike or become confused by the fragrance, while their flowers will help to attract pollinators and beneficial predators.

Companion planting is a great idea for smaller spaces too. The idea of combining plants that crop at different times and support each other is fundamental to potager-style veg growing. Why not alternate rows of broccoli with faster growing spinach, beetroot and radish, that also have a reputation for enhancing the flavour of plants in the brassica family?

Sometimes it's a good idea to grow your companion plant a short distance away from your crop to draw the pests away. You might have to treat this as a sacrificial plant that you don't mind becoming infested with blackfly or other caterpillars. For example, if you grow nasturtiums away from your brassicas, cabbage white butterflies will lay their eggs on them which keeps the caterpillars away from your cabbages, kales and sprouts. In turn, the birds will feed on the pesky grubs. So, it becomes a very virtuous circle of growth and life.

It's a beautiful natural method for dealing with unwanted pests and diseases and by using companion plants, you're creating an organic, balanced ecosystem that will only benefit your garden, and encourage great food crops and flowers.

The garlicky scent of these small, white-flowered members of the allium family will put off and confuse the dreaded carrot fly that is drawn to the scent of young carrot seedlings.

It might seem a strange combination but why not plant a low-growing hedge of lavender around your bed of leeks? Leeks are ready to harvest from late summer and meanwhile, the scented lavender will look great, buzzing with bees and protecting the leeks by confusing allium moth and allium leaf miners that would ordinarily be drawn to the oniony smell.

The sunny golden and orange flowers of nasturtium will lure aphids away from the beans and also attract the good guys that prey on aphids. Plant a nasturtium patch or grow in pots nearby to divert the attention of the insects away from your beans.

Most members of the brassica family like kale will benefit from growing alongside strongly scented herbs such as sage, rosemary, and mint, which can help to deter or distract common pests like flea beetle and cabbage root fly.

Many growers swear that borage improves the flavour of strawberries if grown alongside them. Borage leaves have a cucumber flavour which complements the strawberries – it certainly makes a good combination in your summer Pimms. However, the blue starry flowers are also a magnet for summer pollinators so these will help to ensure a good crop of strawberries.

These fit together in terms of size and growing requirements. Cucumbers need lots of space and nutrients while nasturtiums will happily fit in wherever they can. They are also reputed to be good at repelling cucumber beetles which will damage the plants and will attract other friendlier insects that prey on them.

Aside from being a pretty companion, the innocuous white flowers of sweet alyssum keep coming all summer long, and can help to defend potato crops from pests such as white grubs, wireworms, potato beetle and leafhopper by attracting wasps and other insects that feed on them. These low-growing annual bedding plants also help to keep weeds at bay and stop the soil from losing moisture.

It's not only a great tasting combination on the plate, but many gardeners swear that by growing them together, basil can enhance the flavour of the tomatoes too. Easy bedfellows, they both require the same growing conditions – plenty of sun, fertile soil and liquid feed through the summer. The basil will also draw in beneficial insects to aid pollination of the tomato flowers.

Broad beans are a great crop to grow, but are prone to black fly infestations in early summer that can decimate crops and dent your gardener's morale. Summer savoury has a reputation for repelling these pests and it has a dual role as the flavour complements broad beans when cooked together, so it's a good companion on plot and plate.

Plant out your garlic cloves in winter leaving space for your aubergines, peppers and chilli plants to plant out in between rows when the weather is warm enough. Garlic will help to deter pests large and small, from aphids to deer and rabbits, and it also helps as an anti-fungal agent, so gives some protection against these airborne diseases.

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