Why Are My Turnip Leaves Curling?

Flea beetle

Flea beetle (Phyllotreta species) is the most serious pest of turnip seedlings in UK gardens. The small, shiny, black or striped beetles jump when disturbed and chew numerous small, round holes in the leaves of seedlings from germination onward. Heavily attacked seedlings become riddled with holes, curl their leaves, and may die if the beetles are numerous enough. Adult flea beetles overwinter in leaf litter and soil and are most active in warm, dry conditions from April to June, which coincides exactly with the period of spring turnip sowings.

What to do

• Cover turnip sowings with fine insect mesh immediately after sowing and secure the edges firmly. This is the single most effective protection against flea beetle and also retains soil warmth and moisture, which helps seedlings establish quickly enough to outgrow beetle attacks.
• Water seedlings regularly during dry periods: flea beetles are far less active when the soil surface is moist, and well-watered seedlings recover from minor attacks more quickly.
• Sow thickly so that even if some seedlings are badly attacked, enough survive to produce a crop. Thin to the final spacing once the seedlings are large enough to withstand beetle attack.

Downy mildew

Downy mildew (Peronospora parasitica) causes pale, yellowish, angular patches on the upper surface of turnip leaves, with a grey-purple, downy fungal coating on the underside of the patches. Affected leaves may curl and pucker around the infection sites. The disease is most severe in cool, wet conditions with poor airflow, and is particularly damaging on closely spaced seedlings where leaves remain wet for extended periods.

What to do

• Remove and destroy affected leaves promptly to reduce spore spread through the crop. The disease spreads via airborne spores and is fastest in humid, crowded plantings.
• Thin seedlings to the appropriate spacing as soon as they are large enough to handle: adequate spacing dramatically improves airflow and reduces the microclimate humidity that favours downy mildew development.
• Rotate brassica crops each year to different beds to reduce the soil inoculum. Downy mildew oospores can persist in soil for several years.

Cabbage aphid

Cabbage aphid (Brevicoryne brassicae) forms dense, grey-green, waxy colonies on the underside of turnip leaves and on the growing tips, causing the leaves to curl inward around the colonies. The aphids are distinctive in their tight, compact, waxy clusters and their grey-blue colouration. Heavy infestations stunt growth and reduce root development. Cabbage aphid spreads rapidly and can build up large populations quickly in warm summer conditions.

What to do

• Squash small colonies by hand as soon as they are noticed. The waxy coating of cabbage aphid makes contact insecticides less effective than on uncoated species; thorough coverage of the underside of leaves is essential for any spray to work.
• Apply insecticidal soap or pyrethrin-based spray, ensuring full coverage of the underside of leaves where colonies concentrate. Repeat applications every 5 to 7 days until the infestation is controlled.
• Remove and destroy any turnip plants with large, established aphid colonies in the centre of the growing tip, as these are difficult to eradicate and the plant is already significantly stressed.

Clubroot

Clubroot (Plasmodiophora brassicae) does not cause leaf curl directly but causes wilting, yellowing, and collapse of brassica plants including turnips, which can be confused with drought or pest attack. The definitive sign is the characteristic large, distorted swellings (clubs) on the roots, clearly visible when a wilting plant is pulled from the ground. Clubroot persists in the soil for 20 years or more and severely affects all brassica family crops in infected beds.

What to do

• If clubroot is confirmed, avoid growing any brassica family crop (turnips, swede, cabbage, broccoli, kale, radishes) in that bed permanently if possible.
• Lime the soil to raise the pH to 7.5 or above: clubroot is suppressed in alkaline soil. Apply lime in autumn and test the pH before sowing.

Drought

Turnip leaves wilt and curl in hot, dry conditions, and the roots of drought-stressed turnips become woody, pithy, and bitter rather than the sweet, crisp texture expected at harvest. Turnips bolt (run to seed) readily in hot weather, producing a tall flower stem and making the root inedible. Regular watering in dry conditions is essential, particularly for spring and summer sowings when hot weather coincides with rapid plant development.

What to do

• Water turnips consistently during dry periods, aiming to keep the soil evenly moist at all times. Irregular watering that allows the soil to dry out and then be flooded causes split, cracked roots.
• Harvest summer turnips while they are small (golf-ball to tennis-ball size): small roots are sweeter and more tender, and delaying harvest in warm weather increases the risk of bolting and pithy roots.

Frequently asked questions

Why are my turnip leaves curling?

Turnip leaves curl most often from flea beetle damage, downy mildew, or cabbage aphid infestation. Flea beetle (Phyllotreta species) creates small, round shot-holes in the leaves of turnips and other brassicas; heavily attacked seedlings curl their leaves as a stress response and may fail to establish. Downy mildew (Peronospora parasitica) causes pale, angular patches on the upper leaf surface with grey-purple mould on the underside, leading to yellowing and curling. Cabbage aphid (Brevicoryne brassicae) feeds in dense waxy colonies on the underside of leaves, causing curling and distortion around the feeding sites.

How do I control flea beetle on turnips?

Flea beetle is the most damaging pest of turnip seedlings in UK gardens. The beetles jump away when disturbed (hence the name) and chew small, round holes in the leaves of seedlings, which can kill young plants if attacks are severe. The best protection is to cover turnip sowings with insect-proof mesh (fine mesh rather than the standard cabbage caterpillar mesh, as flea beetles are small) immediately after sowing and keep the mesh in place until the plants are well established. Growing under mesh also retains soil moisture, which reduces beetle activity (flea beetles are most active in hot, dry conditions). Keeping the seedbed watered and the plants growing vigorously helps them outgrow flea beetle damage more quickly.

Can I eat turnip leaves?

Turnip leaves (called turnip tops or turnip greens) are completely edible and highly nutritious, with a flavour similar to spring greens or mustard greens. Young, tender turnip leaves can be eaten raw in salads; older or larger leaves are best cooked lightly, stir-fried, or added to soups and stews. Turnip tops are a traditional winter green in many parts of the UK and Europe, often harvested when the ground is too frozen to lift root vegetables. Some turnip varieties are grown specifically for their leaves rather than their roots, particularly Italian varieties such as 'Cima di Rapa' (also known as rapini or broccoli rabe).

When should I sow turnips in the UK?

Turnips can be sown in the UK from March to August for a succession of harvests. Early sowings from March to May produce small, sweet roots for summer harvests; main-crop sowings from July to August produce larger roots for autumn and winter use and for turnip tops in late winter and spring. Turnips prefer cool conditions and bolt (run to seed) in hot weather, so midsummer sowings in exposed positions sometimes fail; a sowing from late July to early August once the hottest summer weather has passed is often more successful than a June sowing. Turnips grow quickly and can be ready to harvest in 6 to 10 weeks depending on variety and conditions.