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UK Garden Planner
Companion planting is the practice of growing certain plants in close proximity because they benefit each other — by deterring pests, attracting beneficial insects, improving soil, or making better use of space. It has been used by gardeners for centuries and is one of the most effective organic strategies for a productive UK veg patch. The key is knowing which plants are friends and which are foes — and that relationship is specific to each plant.
Basil is the classic tomato companion — it is believed to repel aphids and whitefly while improving the flavour of the fruit. Marigolds (French, not African) deter whitefly and nematodes. Keep tomatoes away from fennel, brassicas and potatoes — the latter share blight.
Leeks and onions are excellent carrot companions — their strong smell confuses the carrot root fly. Rosemary and sage also help deter carrot fly. Avoid planting carrots near dill or parsnips which can attract similar pests.
Marigolds, nasturtiums and dill all help brassicas by attracting beneficial insects that prey on cabbage white caterpillars and aphids. Celery planted nearby is said to deter cabbage white butterflies. Keep brassicas well away from strawberries and tomatoes.
The classic "Three Sisters" combination — beans, courgette and sweetcorn — works well in UK summers. Beans fix nitrogen into the soil, benefiting hungry neighbours. Keep beans away from onions and garlic which are thought to inhibit their growth.
Nasturtiums make excellent companions for courgettes — they attract aphids away from the main crop (acting as a trap plant) while also attracting hoverflies that eat aphids. Borage attracts pollinators which improves fruit set.
Select any plant from the list to see its full companion guide — every friend and foe explained, with the reason why. Or select two plants to instantly check whether they are compatible, borderline, or incompatible. The checker covers over 70 UK vegetables, herbs, fruits and flowers — from alliums to zucchini. Use the results alongside the veg patch planner which shows live companion warnings as you arrange your plot.
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