Common Problems Growing Brassicas

Brassicas – like broccoli, cabbage, cauliflower, kale, and Brussels sprouts—are delicious, nutrient-rich, and versatile vegetables in the garden. However, these cooler season crops are also highly susceptible to various pests, diseases, and environmental stressors, making them tricky to grow for beginners and seasoned gardeners alike. Here’s a rundown of the most common problems you might encounter while growing brassicas, along with practical solutions to help keep your garden healthy.

Kale Jardin Ivory

Cabbage Worms & Caterpillars

Problem: The dreaded cabbage worm, along with its relatives like cabbage loopers and moths, are among the most destructive pests for brassicas. They chew holes in leaves, leaving a messy, weakened plant behind and often go undetected because they blend in with the foliage.

Solution:

• Hand-picking: Check your plants regularly, especially the undersides of leaves, and remove any worms you find.
• Row covers: Using lightweight, breathable row covers can act as a physical barrier, preventing moths from laying eggs on your plants.
• Natural predators: Encourage beneficial insects like ladybugs, lacewings, and parasitic wasps, which feed on these pests.

Purple Sprouting Broccoli Rudolph

Clubroot

Problem: Clubroot is a soil-borne fungal disease that causes brassica roots to become swollen and distorted. Plants with clubroot struggle to take up water and nutrients, leading to stunted growth, yellowing leaves, and eventual wilting.

Solution:

• Soil pH adjustment: Clubroot thrives in acidic soil. Liming the soil to raise the pH above 7.0 can help prevent it.
• Crop rotation: Since clubroot spores can remain in the soil for years, avoid planting brassicas in the same spot more than once every three to four years.
• Improve drainage: Waterlogged soil exacerbates clubroot, so ensure good drainage or consider raised beds in areas prone to heavy rains.

Savoy Cabbage Aubervilliers

Aphids

Problem: Aphids are small, sap-sucking insects that often cluster around new growth and leaf undersides. They weaken plants by feeding on their sap, spreading diseases, and secreting sticky honeydew, which can encourage mould growth.

Solution:

• Blast with water: A strong stream of water can dislodge aphids from leaves, though you may need to repeat this frequently.
• Companion planting: Plants like marigolds or nasturtiums can repel aphids, while planting flowers like calendula, attracts predators like ladybugs and hoverflies.

Cauliflower Sicilian Violet

Bolting

Problem: Bolting happens when brassicas start to flower prematurely. It’s most common in leafy greens like kale, but it can affect all types of brassicas, leading to bitter-tasting or woody leaves.

Solution:

• Plant at the right time: Brassicas are cool-season plants, so planting them during the hottest months can increase bolting risk. Aim to grow them in early spring or autumn when temperatures are moderate.
• Shade protection: A little shade can help cool the soil and prevent stress during hotter periods.
• Consistent watering: Ensure the soil is consistently moist (but not waterlogged) to avoid stress that can lead to bolting.

Brussel Sprout Red Bull

Downey Mildew

Problem: Downy mildew is a fungal-like disease that causes yellow spots on leaves, often with a fuzzy greyish or purplish mould on the undersides. It thrives in cool, damp conditions and can cause serious damage to brassicas.

Solution:

• Reduce moisture: Water brassicas at the base of the plant to keep foliage dry, and avoid overhead watering.
• Proper spacing: Plant brassicas with adequate space between them to promote good airflow, which helps prevent mildew.
• Remove infected leaves: Prune off any affected leaves to help limit the spread, and dispose of them away from the garden.
• Rotate crops: Like many fungal diseases, downy mildew can live in soil, so avoid planting brassicas in the same area for several years.

Cabbage Holland Late Winter

Black Rot

Problem: Black rot, a bacterial disease, causes leaves to yellow and wilt, forming dark V-shaped lesions on leaf edges. It can be particularly destructive in warm, wet conditions, spreading rapidly through soil, water, and even tools.

Solution:

• Avoid overhead watering: Bacteria can spread through water, so water plants at the base whenever possible.
• Remove infected plants: Promptly remove any plants that show signs of black rot and dispose of them away from the garden.
• Seed treatment: If you save seeds, treat them with hot water to kill any bacteria. Starting with disease-free seeds is one of the best preventative measures.
• Crop rotation and sanitation: Avoid planting brassicas in infected soil and sterilise tools to prevent spreading the bacteria to other plants.

Kohlrabi Dyna

With these solutions, you’ll be better prepared to handle the most common brassica growing issues and enjoy a healthy, productive garden. Happy growing!