Companion Planting UK Guide

This post may contain affiliate links. If you make a purchase through these links, we may earn a commission at no additional cost to you.

Picture a classic British garden. It’s probably a cheerful jumble of flowers, herbs, and vegetables, all rubbing shoulders in a way that just feels… right. Bees are buzzing, ladybirds are on patrol, and the whole space hums with life. This isn’t just a happy accident. This is the magic of companion planting, an age-old secret that’s less about strict rules and more about creating a thriving, cooperative community right in your back garden or allotment.

At its heart, companion planting is simply about pairing plants that help each other out. Think of it like a clever seating plan at a dinner party. You wouldn’t sit two rivals next to each other, would you? Instead, you’d place friends together, knowing they’ll have a good chat and look after one another. In the garden, this means growing certain plants side-by-side to deter pests, attract helpful insects, improve the soil, and even make each other taste better.

It’s an approach that swaps chemical sprays for clever partnerships, turning your garden into a self-regulating ecosystem. Whether you’ve got a sprawling veg patch or a few pots on a balcony, understanding these plant friendships can completely transform the way you grow. So, let’s dig in and explore how you can get your plants working together for a healthier, happier, and more bountiful harvest.

Core Concepts: What on Earth is Companion Planting?

Companion planting sounds complex, but the ideas behind it are surprisingly simple. It’s all about creating a balanced little world where plants, insects, and soil work in harmony. You’re basically becoming a matchmaker for your garden, setting up partnerships that benefit everyone involved. These partnerships work in several clever ways.

Pest Control Pals: The Bouncers of the Veg Patch

One of the biggest headaches for any gardener is pests, from pesky aphids to munching caterpillars. Companion planting offers a brilliant, natural solution. Some plants act like bouncers, kicking unwanted guests out of the garden club.

Scent Confusion: Many pests find their favourite snacks by smell. Strong-smelling herbs like rosemary, lavender, mint, and sage can mask the scent of tasty vegetables like carrots and cabbages. The carrot fly, for instance, struggles to sniff out carrots when the air is full of the scent of rosemary. It’s like trying to find a chip shop in a perfume factory.
Natural Repellents: Some plants contain natural chemicals that pests simply can’t stand. French marigolds are the superstars here. They release a substance from their roots that repels nematodes, tiny worms that can devastate the roots of tomatoes and beans. Planting a border of marigolds is like putting up a “No Entry” sign for these underground nuisances. Similarly, garlic and chives can help deter aphids from roses and lettuces.

Beneficial Bug Buddies: Inviting the Good Guys In

Not all insects are villains. Many are heroes, and companion planting is your way of sending them an invitation. Ladybirds, lacewings, and hoverflies are the garden’s cavalry, happily munching on aphids and other pests.

To attract these good guys, you need to offer them something they love: nectar and pollen. Plants with small, open flowers are perfect for this.

Umbellifers: This family of plants, which includes dill, fennel, parsley, and coriander, produces umbrella-shaped clusters of tiny flowers. These are a five-star hotel for hoverflies and parasitic wasps (the good kind that lay their eggs in caterpillars!).
Compositae: Flowers like calendula (pot marigolds) and cosmos are not just pretty faces. They are magnets for beneficial insects, drawing them into your garden to help keep pest populations in check.

The Bodyguards: Taking One for the Team

Sometimes, the best defence is a good sacrifice. This is the idea behind “trap cropping.” You plant something that pests find absolutely irresistible, deliberately luring them away from your prized vegetables.

The classic example is using nasturtiums. Aphids, especially blackflies, adore nasturtiums. If you plant them near your broad beans, the aphids will swarm the nasturtiums, leaving your bean crop largely untouched. You can then simply remove the infested nasturtium leaves and dispose of them, aphids and all. It’s a cunning and surprisingly effective tactic.

Soil Mates: The Underground Support Network

What happens below the ground is just as important as what happens above it. Healthy soil means healthy plants, and some plant partnerships are fantastic for improving the earth they grow in.

Nitrogen Fixers: Plants need nitrogen to grow strong, leafy greens. While it’s abundant in the air, most plants can’t use it directly. This is where the legume family—peas, beans, and clover—comes in. They have special nodules on their roots that house bacteria capable of taking nitrogen from the air and “fixing” it into a form plants can use. When you grow them next to nitrogen-hungry plants like cabbages or sweetcorn, they act like a slow-release fertiliser, enriching the soil for their neighbours.
Dynamic Accumulators: Some plants have deep taproots that can “mine” for nutrients deep down in the soil. Comfrey and borage are brilliant at this. They pull up minerals like potassium and calcium that other, more shallow-rooted plants can’t reach. When their leaves die back and decompose, these nutrients are released into the topsoil, ready for their neighbours to use.

Supportive Friends: A Helping Hand

Finally, some plant pairings are just about good structure and creating a happy environment. This is best shown by the famous “Three Sisters” method, a technique used by Native American peoples for centuries.

Sweetcorn grows tall, providing a natural pole for the beans to climb.
Climbing beans grow up the sweetcorn, and as legumes, they fix nitrogen in the soil, feeding the hungry corn.
Squash spreads out across the ground. Its large leaves act as a living mulch, suppressing weeds and keeping the soil cool and moist.

It’s a perfect, self-sufficient system where each plant supports the others. You can create similar systems on a smaller scale, for example, by growing lettuces in the shade of taller sweetcorn or peas to protect them from the harsh midday sun.

Historical Development: From Cottage Gardens to Climate Action

The idea of companion planting isn’t a newfangled trend. It’s an ancient wisdom, born from centuries of observation by farmers and gardeners. Long before we had science labs and textbooks, people understood that some plants just grew better together.

This knowledge was at the heart of the traditional British cottage garden. These weren’t just for show; they were productive plots where flowers, herbs, and vegetables were all mixed in together. A cottage gardener would notice that the roses seemed healthier when garlic was planted at their base, or that fewer caterpillars plagued the cabbages when mint was growing nearby. This wasn’t superstition; it was practical, hands-on science passed down through generations.

The practice was formalised in the 20th century with the rise of the organic and biodynamic movements. As industrial agriculture began to rely heavily on chemical fertilisers and pesticides, a counter-movement looked for more natural, holistic ways to grow food. Gardeners and writers in the UK began to document these traditional pairings, sharing knowledge through magazines and books. They gave a name to what cottage gardeners had always known: companion planting.

Today, this ancient practice has never been more relevant. As we face challenges like climate change and biodiversity loss, companion planting offers a simple but powerful way for every gardener to make a positive impact. It’s a way of working with nature, not against it, to create gardens that are resilient, productive, and buzzing with life.

The A-Z of Companion Planting: Your Ultimate British Garden Guide

Now for the really practical bit. What should you actually plant next to what? Here’s a guide to some of the most common British garden plants and their best friends (and worst enemies).

The Veg Patch All-Stars

This is where companion planting really shines, helping you get bigger and better harvests.

Tomatoes

Tomatoes are a garden staple, but they can be prone to pests like whitefly and greenfly.

Best Friends: Basil is the tomato’s ultimate companion. It’s said to repel whiteflies and tomato hornworms, and many gardeners swear it even improves the tomato’s flavour. French marigolds are another must-have, protecting the roots from nematodes. Chives and garlic can help deter aphids.
Bad Neighbours: Keep tomatoes away from the brassica family (cabbage, broccoli, etc.) as they can stunt each other’s growth. Also, avoid planting them near potatoes, as both are susceptible to blight, a disease that can spread rapidly between them.

Potatoes

A beloved crop, but one that can exhaust the soil.

Best Friends: Beans and peas are great companions as they fix nitrogen, enriching the soil for the hungry potatoes. Horseradish is traditionally planted at the corners of a potato patch to deter the potato beetle. Sweetcorn can provide some welcome shade during hot afternoons.
Bad Neighbours: Avoid planting potatoes near sunflowers or squash, as they can inhibit the spuds’ growth. Keep them away from tomatoes to reduce the risk of blight.

Brassicas (Cabbage, Broccoli, Cauliflower, Kale)

This family is a favourite of many pests, especially the cabbage white butterfly.

Best Friends: Your best defence is strong-smelling herbs. Rosemary, thyme, sage, and mint (always plant mint in a pot to stop it spreading!) can confuse the cabbage white butterfly, making it harder for it to find your plants. Onions and leeks also work well as scent-maskers. Nasturtiums are a brilliant trap crop for aphids.
Bad Neighbours: Keep them away from strawberries and tomatoes.

Root Veg (Carrots, Parsnips, Beetroot)

The biggest challenge here is often underground pests or flying foes.

Best Friends: The partnership between carrots and leeks is a classic. The smell of the leek deters the carrot fly, while the smell of the carrot deters the leek moth. It’s a perfect alliance. Rosemary and sage also help to repel the carrot fly. For beetroot, planting onions or kohlrabi nearby can be beneficial.
Bad Neighbours: Avoid planting carrots near dill or fennel, as they can attract pests that also trouble carrots.

Salad Greens (Lettuce, Spinach)

These tender leaves need protection from both pests and the sun.

Best Friends: Chives and mint can help repel slugs and aphids, the two main enemies of lettuce. Taller plants like beans and sweetcorn can provide welcome shade, preventing your lettuce from bolting (flowering prematurely) in hot weather. Radishes are another good companion, as they are harvested before the lettuce gets big, loosening the soil.
Bad Neighbours: There aren’t many plants that actively dislike lettuce, but avoid planting it with anything that will completely overshadow it and block out all light.

The Herb Garden: The Garden’s Superheroes

Herbs are the engine room of a companion-planted garden. Most of them are brilliant at attracting beneficial insects and repelling pests.

Mint: A pest-repelling powerhouse, great near brassicas and tomatoes. But BE WARNED! Mint is incredibly invasive. Always plant it in a container sunk into the ground to stop its roots from taking over your entire garden.
Rosemary: Fantastic for protecting carrots and cabbages. It’s a hardy perennial that will provide protection year after year.
Basil: The best friend of tomatoes, but also good near peppers and aubergines.
Borage: This is a magnet for bees and other pollinators. Plant it near strawberries, squash, and tomatoes to improve pollination and get more fruit. It’s also a “dynamic accumulator,” mining nutrients from the soil.
Chamomile: Known as the “plant doctor,” chamomile is said to boost the health and vigour of any plant it’s near.

The Fruit Cage & Flower Border

Companion planting isn’t just for vegetables. You can use it to get better fruit yields and healthier flowers too.

Strawberries: Plant borage nearby to attract pollinators and strengthen the plants. Onions and spinach are also good companions.
Roses: The classic companion for roses is garlic. It helps to repel aphids and is thought to reduce the incidence of black spot, a common fungal disease. Lavender and catmint also work well.
Sunflowers: While they can inhibit the growth of potatoes, sunflowers are great companions for climbing beans, providing a strong, natural trellis for them to scramble up.

Practical Applications and Tips: Getting Your Hands Dirty

Knowing the theory is one thing, but how do you put it into practice? Here are some simple tips for designing your own companion-planted garden.

1. Plan Before You Plant

Don’t just scatter seeds randomly. Take a piece of paper and sketch out your garden or allotment.

Think in Groups: Instead of planting a whole row of just one vegetable, try interplanting. This means mixing different plants together in the same bed. A row could look like this: Leek – Carrot – Leek – Carrot. This immediately helps to confuse pests.
Consider Height and Light: Place taller plants like sweetcorn and climbing beans at the back of your beds (usually the north side) so they don’t shade out smaller, sun-loving plants like lettuce and radishes.
Integrate Flowers and Herbs: Don’t keep your veg, herbs, and flowers separate. Dot French marigolds throughout your tomato bed. Plant a border of rosemary around your carrot patch. Mix calendula in with your brassicas. This creates a diverse and resilient ecosystem.

2. Know the Bad Neighbours

Just as important as knowing what to plant together is knowing what to keep apart. Here are a few key rivalries to remember:

Potatoes and Tomatoes: Both are in the nightshade family and susceptible to the same blight.
Onions and Beans/Peas: Onions and other alliums can release a substance that inhibits the growth of legumes.
Fennel: Fennel is a bit of a bully and is best grown on its own. It can inhibit the growth of most other plants, especially tomatoes and beans.

3. A Sample Companion Planting Bed

Here’s an idea for a 1.2m x 2.4m (4ft x 8ft) raised bed, a common size in British gardens:

Back (North)	Middle	Front (South)	Edges
Sweetcorn with Climbing Beans up them	Tomatoes interplanted with Basil plants	A row of Lettuces interplanted with Radishes	A border of French Marigolds all around
A row of Leeks	A row of Carrots	A row of Spinach	A pot of Mint sunk into one corner

This design incorporates several companion planting principles: the “Three Sisters” (in a simplified form), scent confusion for the carrots, pest repellents for the tomatoes, and a trap for slugs and aphids away from the lettuce.

4. Tackling British Problems: Slugs!

Slugs are the bane of many a British gardener. While no single plant will create a magic forcefield, some companion planting strategies can help.

Encourage Predators: Create habitats for slug-eaters like thrushes, hedgehogs, and frogs. A small pond or a log pile can make a huge difference.
Repellent Herbs: Some gardeners find that a border of mint or chives can deter slugs from munching on tender lettuces.
Sacrificial Plants: Slugs often prefer dying or weak foliage. Keeping your garden tidy and removing any decaying leaves can make it less attractive to them.

Future Implications: The Garden of Tomorrow

Companion planting is more than just a charming gardening technique. It’s a glimpse into a more sustainable future for how we grow our food. The principles of diversity, cooperation, and working with nature are being scaled up by innovative farmers to create “polyculture” systems that are more resilient to pests, diseases, and a changing climate.

By practising companion planting in our own gardens, we are doing more than just growing vegetables. We are nurturing biodiversity, reducing our reliance on chemicals, and re-learning an ancient wisdom that sees a garden not as a factory, but as a community. Every time you plant a marigold next to a tomato, you are casting a vote for a healthier planet.

So next time you’re planning your garden, don’t just think about what you want to eat. Think about who your plants want to live next to. By fostering these friendships, you’ll be rewarded with a garden that is not only more productive but also a more vibrant and fascinating place to be.