You plant out sturdy young kale and broccoli, and a month later they're lace, or bare stalks, or sitting there stunted and wilting on a warm afternoon. Three problems cause nearly all of it: cabbage white caterpillars, wood pigeons and clubroot. The first two have one simple fix, a net put on the day you plant. The third has no cure, so you work around it.
01At a glance
- Net at planting: fine mesh over hoops, kept clear of the leaves, and left on. The RHS says to cover broccoli "at all times".
- Caterpillars: butterflies and moths are most active from May to October. Check under leaves for eggs.
- Pigeons: netting or a fruit cage is the only reliable answer. Scarers work briefly at best.
- Clubroot: no chemical treatment is available to gardeners. Lime acid soil, start plants in pots, keep infected soil from spreading.
- Plant firm: tread the soil before planting and set plants in deep, with the lowest leaves at soil level.
02One net for butterflies and pigeons
The RHS kale and broccoli guides both recommend fine-mesh netting or insect-proof mesh on hoops or canes. It keeps out the egg-laying butterflies and the pigeons in one go. A coarse pigeon net stops pigeons but lets butterflies straight through.
- Put hoops or canes in first, tall enough that the mesh won't rest on the plants as they grow. Broccoli grown for winter can reach 90cm.
- Keep the mesh off the leaves. The RHS warns that butterflies can lay eggs through netting that touches the plant.
- Pull it taut and weigh down the edges. The RHS asks you to check nets regularly for holes so that birds and other animals don't get trapped.
- Leave it on through winter for purple sprouting broccoli and kale. Pigeons feed hard on winter brassicas when snow or frost covers their other food. The RHS notes they often feed in the early morning, when you won't see them.
03Caterpillars: know what you're looking at
The RHS names three main culprits:
- Large white butterfly: clusters of yellow, skittle-shaped eggs on either side of the leaf. Caterpillars in June–July and again August–September.
- Small white butterfly: single yellow eggs, laid on the undersides of leaves.
- Cabbage moth: clusters of white, round eggs. Caterpillars from July to September.
If anything gets under the net, check plants regularly and pick off eggs and caterpillars by hand. Tolerating a few also helps the birds and parasitic wasps that eat them.
04Clubroot: the one you can't cure
Clubroot is a soil-borne disease of the cabbage family. The RHS says its resting spores can survive in soil for up to 20 years, and there is nothing available to gardeners that kills it. You manage it by making the soil less favourable and by giving young plants a head start.
- Lime acid soil. The RHS suggests 500g per square metre on acid ground, then lighter dressings of 270g per square metre in later years. Broccoli likes a pH of about 6 to 7. Raising the pH reduces clubroot. It doesn't get rid of it.
- Improve drainage. Raised beds help. Most new infections happen from midsummer to late autumn, when the soil is warm and moist.
- Raise plants in pots before planting out. The RHS suggests pots at least 9cm across, so plants go out with a large, healthy root system.
- Grow resistant varieties where they exist. The RHS lists calabrese 'Komodo' and 'Monclano', plus resistant cabbages, cauliflowers and sprouts. It doesn't list a resistant kale. Resistance is partial, not complete.
- Don't bring it in. Buy brassica plants only from a clubroot-free source, and be wary of spare plants from friends. Clean soil off boots, tools and barrows.
Rotating crops is still good practice, and the RHS kale guide recommends it. But with spores lasting 20 years, moving brassicas around a small plot won't starve them out on its own.
05Is it clubroot or just thirst?
Clubroot plants are stunted, often with purplish leaves, and wilt in hot weather but perk up again when it cools. That looks a lot like a dry plant. To check, lift one: clubroot roots are swollen and distorted, with few fine roots. If the roots look normal, water steadily. Our broccoli profile covers watering.
06Plant firm
Brassicas planted in loose, freshly dug soil rock about and do badly. Tread the bed down with small shuffling steps first, then rake it level. Plant deeper than the plants sat in their pots, with the lowest leaves at the soil surface, and water well. Earth up or stake tall broccoli before the autumn gales. Our kale profile covers spacing and picking.
Before planting where children or pets play, check the safety flags on our kale profile and broccoli profile.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: RHS — Cabbage caterpillars · RHS — Pigeons · RHS — Club root · RHS — How to grow kale · RHS — How to grow broccoli
Checked 8 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.