Clubroot: identify, prevent, control

Worst in warm, wet, acidic soils through the main brassica seasons, but the long-lived spores are a risk year-round.

Clubroot is a soil disease that swells and distorts brassica roots into clubbed lumps, choking the plant's water uptake. It persists in the soil for many years and loves acidic, wet ground, so once it arrives it shapes how you grow brassicas for a long time.

How to identify it

• Brassicas wilting in the heat and recovering overnight
• Stunted, yellowing plants that never thrive
• Swollen, clubbed and distorted roots when you lift a plant
• Whole patches of brassicas affected in the same bed

How to prevent it

• Rotate brassicas on a long cycle and never replant them into infected ground
• Lime the soil to raise the pH towards 7, since clubroot hates alkaline conditions
• Improve drainage, as the disease thrives in wet soil
• Raise your own seedlings in clean mix and never bring in infected plants or soil

Organic control, step by step

• Remove and bin affected plants with their roots, never composting them
• Lime the bed well ahead of planting to push the pH up
• Improve drainage with raised beds and added organic matter
• Rest the bed from brassicas for several years, since spores survive a long time
• Clean tools and boots to avoid carrying infected soil to clean beds
• Grow clubroot-resistant brassica varieties where available

Plants it attacks