Introduction
Companion planting UK advice can feel confusing at first.
Most of the articles online are generic or not tailored to British allotments. So if you’ve been searching for what grows well together in a British vegetable garden without the myths and magic fixes, you’re in the right place.
This guide focuses specifically on companion planting UK conditions: damp summers, tight bed spacing, carrot fly, cabbage white, and everything in between. Rather than repeating generic theory, we’ll focus on what actually works for UK veg growers.
What Is Companion Planting (In Simple Terms)?
Put simply, companion planting means growing certain crops side by side because they support each other in some way.
In practical terms, that usually involves:
- Improving space efficiency
- Managing pest pressure
- Increasing biodiversity in smaller beds
In most UK gardens, companion planting helps by:
- Confusing or deterring pests
- Attracting beneficial insects
- Making better use of limited bed space
- Reducing direct competition between crops
In other words, use companion planting as a support strategy. Let it strengthen a well-managed bed rather than trying to fix underlying problems.
Does Companion Planting Actually Work?
Companion planting means growing different crops close together because they benefit each other in some way.
For instance, planting basil with tomatoes is widely recommended in many companion planting guides. It can attract beneficial insects and help you use bed space efficiently. But it won’t magically prevent tomato blight during one of our damp British summers.
That does not mean however, that companion planting doesn’t work.
In fact, Companion planting helps strengthen a healthy garden ecosystem — but, it does not replace solid gardening fundamentals. It is more of a way to help squeeze the best out of every growing season by planting things that complement each other, close by.
The Royal Horticultural Society (RHS) notes that while some plant pairings can help, good growing practices remain more important than companion theory.
What Companion Planting Can do
When you use companion planting realistically, it can:
- Improve biodiversity
- Reduce the impact of pests
- Help you manage space more efficiently
- Support soil structure
What Companion Planting Can’t do
Just as importantly, companion planting cannot:
- Fix overcrowded beds
- Stop blight during prolonged wet weather
- Replace crop rotation
- Repair poor soil structure
The Companion Plants Chart and Cheat Sheet
This companion plants chart focuses on the vegetables most allotment growers grow in the UK.
Use it as a working reference while planning your beds. Then adjust based on spacing, sunlight, airflow, and crop rotation, because those fundamentals still matter more than any single companion pairing.
Companion Planting Quick Table
This companion planting cheat sheet shows clearly which crops grow well together — and which ones are better kept apart. I have only added the most common crops here, below the table you can download a more comprehensive companion planting guide (for free).
| Crop | Grows Well With | Avoid Planting Near | Quick Notes |
|---|---|---|---|
| Tomatoes | Basil, lettuce, carrots, marigolds | Potatoes, fennel | Prioritise airflow to reduce blight risk |
| Potatoes | Beans, cabbage family (spaced) | Tomatoes | Rotate yearly to reduce disease |
| Carrots | Onions, leeks, chives | Parsnips | Alliums may help reduce carrot fly |
| Onions | Carrots, beetroot, lettuce | Beans, peas | Alliums and legumes don’t mix well |
| Garlic | Brassicas, strawberries | Beans, peas | Works well as a defensive edging crop |
| Peas | Carrots, radish, spinach | Onions, garlic | Give support and allow good airflow |
| Beans (French/Runner) | Sweetcorn, squash | Onions, garlic | Protect young plants from slugs |
| Brassicas (Cabbage/Kale) | Onions, dill, nasturtium | Strawberries | Netting is usually more reliable than flowers |
| Cucumbers | Nasturtium, dill | Potatoes | Shelter and warmth improve UK results |
| Courgette / Squash | Sweetcorn, beans | Potatoes | Allow plenty of space at maturity |
| Sweetcorn | Beans, squash | Tomatoes | Plant in blocks for proper pollination |
| Lettuce | Radish, carrots, spring onions | Overcrowded brassicas | Ideal gap-filling crop |
| Spinach / Chard | Peas, beans | Potatoes | Performs better in spring and autumn |
| Beetroot | Onions, lettuce | Pole beans | Thin properly for larger roots |
| Radish | Lettuce, peas | Hyssop | Fast crop for succession sowing |
| Parsnips | Onions, radish | Carrots | Avoid fresh manure |
| Celery | Leeks, brassicas | Carrots | Needs consistent moisture |
| Strawberries | Chives, garlic | Brassicas | Mulch to keep fruit clean |
| Peppers / Chillies | Basil, onions | Fennel | Grow in sheltered UK spots |
| Leeks | Carrots, beetroot | Beans, peas | Firm soil around stems |
Download the Full Printable Companion Planting Chart
If you’d prefer a cleaner version to print and keep in the shed, the full printable companion planting chart expands on everything above.
In addition to the core companion planting UK vegetable table, it includes:
- An extended crop list
- Clear strength ratings (strong / support / avoid)
- Perennial crops
- Flower and herb companions
- Practical UK-specific notes
As a result, you can refer back to it whenever you’re planning beds or adjusting combinations mid-season.
5 Simple Companion Planting Rules for UK Allotments
If you remember nothing else from this companion planting UK guide, remember these five rules.
1. Alliums and Legumes Don’t Mix
This is one of the most reliable companion planting rules — and it’s worth sticking to in any vegetable companion planting UK layout.
Alliums (onions, garlic, leeks, chives) generally don’t pair well with legumes (peas and beans). While the exact science is still debated, many experienced growers notice reduced vigour when they plant them too close together. Therefore, in practical companion planting terms, it’s usually best to keep them apart.
So if you’re asking, can you plant onions and beans together? — I wouldn’t recommend it.
Instead, try pairing:
- Carrots with onions
- Peas with carrots
- Beans with sweetcorn or squash
By separating alliums and legumes, you avoid one of the most common vegetable companion planting clashes.
2. Height and Shade Matter More Than Theory
Companion planting vegetables only works if light actually reaches your crops.
Tall plants like sweetcorn, Jerusalem artichokes, and climbing beans can quickly cast shade across a bed. As a result, lower-growing vegetables struggle, no matter how “good” the companion pairing looks on a companion plants chart.
For example, if you plant sun-loving crops like tomatoes or peppers in the wrong position, no clever combination will fix a lack of sunlight.
Before focusing on what grows well together, always check:
- Mature plant height
- Sun direction across the day
- Airflow between crops
In most UK gardens, poor light and restricted airflow cause more problems than bad companions ever will.
3. Netting Beats Flowers for Brassicas
Many companion planting charts recommend marigolds and nasturtiums for brassicas.
And yes, they can attract beneficial insects and improve biodiversity. However, if cabbage white butterflies are active — which they usually are in the UK — flowers alone won’t protect your crops.
Therefore, for reliable vegetable companion planting UK results:
- Use netting for cabbage, kale, and sprouts
- Then add flowers as a supporting layer
In other words, companion planting supports protection — it doesn’t replace physical pest control.
4. Fill Gaps With Fast Crops
One of the most practical uses of companion planting vegetables is improving space efficiency.
Fast-growing crops like lettuce, radish, and spring onions slot neatly between slower crops such as brassicas or tomatoes. Because they mature quickly, you harvest them before the larger plants need the space.
As a result, you make better use of your beds without overcrowding them.
This approach works especially well in smaller UK allotments, where space is limited and smart planting makes a real difference.
5. Airflow Is Critical in UK Summers
In damp British summers, airflow often matters more than companion choice.
Tomato blight, mildew on courgettes, and fungal diseases in dense beds are common issues. Unfortunately, overcrowding — even with “good companions” from a companion planting chart — increases humidity and disease risk.
So when deciding what grows well together, always leave enough space for:
- Air movement
- Easy access for harvesting
- Proper light penetration
Ultimately, healthy spacing and airflow support successful companion planting UK beds far more than clever combinations alone.
If you follow these five rules, companion planting becomes far more straightforward. Instead of chasing perfect pairings from every companion plants chart you find, you’ll build balanced, manageable vegetable beds that actually perform throughout the season.
Common Companion Planting Mistakes (And How to Avoid Them)
Even the best companion planting plan will struggle if the basics aren’t right. Most problems come from poor spacing, shade, tired soil, or expecting too much from a companion plants chart.
Before blaming the pairing, check these common mistakes.
1. Overcrowding the Bed
Even good companions need space.
Overcrowding leads to:
- Poor airflow
- Higher humidity
- More blight and mildew
- Smaller harvests
Always check the mature size of each crop before planting.
2. Relying on Flowers for Pest Control
Marigolds, nasturtiums, and dill can attract beneficial insects, but they won’t stop serious pest problems on their own.
Cabbage whites will still find brassicas, while slugs will still attack courgettes. Therefore, use flowers alongside netting, barriers, and other physical protection.
3. Ignoring Crop Rotation
Companion planting doesn’t replace crop rotation.
Growing related crops in the same spot year after year can build up pests and disease. Potatoes and tomatoes, for example, share a high risk of blight.
So plan companion crops within a sensible rotation.
4. Planting Fennel Too Close
Fennel doesn’t grow well with many neighbours and may restrict nearby growth.
For that reason, give it its own space, ideally away from the main vegetable beds.
5. Forgetting Root Competition
Not all competition happens above ground.
Crops with similar root depths and feeding needs can compete for water and nutrients. Instead, combine plants with:
- Different root depths
- Different growth speeds
- Different canopy heights
Ultimately, companion planting works best when spacing, airflow, soil, and rotation are already in place. Use it to fine-tune your beds, not to fix underlying problems.
FAQ – Companion Planting UK
Below are some of the most common questions UK veg growers ask about companion planting UK — answered in plain English and based on real allotment experience.
Avoid planting tomatoes beside potatoes because both are vulnerable to blight. Fennel is also best kept separate. Basil, lettuce, carrots, and marigolds make more suitable neighbours, although spacing and airflow still matter most.
Carrots grow well with onions, leeks, chives, lettuce, and radish. Alliums may help confuse carrot fly, while quick crops like radish use the surrounding space without causing much competition.
It’s generally better to keep them apart. Onions and other alliums are widely considered poor companions for beans and peas. Instead, pair onions with carrots or beetroot, and beans with sweetcorn or squash.
Yes, but it works best as a supporting strategy. It can improve biodiversity, use space efficiently, and reduce some pest pressure. However, it cannot replace good spacing, healthy soil, crop rotation, or physical protection.
Keep potatoes away from tomatoes because they share blight risk. Large spreading crops such as squash can also restrict airflow. Beans, spaced brassicas, and calendula usually make better neighbours.
If you’re ever unsure about a pairing, use the companion plants chart above as a quick reference. Alternatively, you can check combinations visually inside the free companion planting planner within the Backyard Farmer Allotment Planner before anything goes in the ground — which is usually the safest approach.
Conclusion: Companion Planting the Practical Way
Companion planting UK-style works best when you keep it simple. Focus first on spacing, airflow, crop rotation, and healthy soil, then use companion planting to support biodiversity, reduce some pest pressure, and make better use of your beds.
Use the companion plants chart above as a quick guide to what grows well together. You can also download the full printable companion planting chart to keep in the shed.
Alternatively, our complete guide to using the Backyard Farmer Allotment Planner in the UK shows you how to test combinations, adjust spacing, and plan rotations before planting.
Keep it practical, and let companion planting support your growing rather than complicate it.
