Why Are My Coriander Leaves Curling?

Bolting

Bolting is by far the most common reason coriander leaves change shape and appear to curl or wither in UK gardens. Coriander is a fast-maturing annual that detects long days and warm temperatures as a signal to flower and set seed. When it bolts, the plant rapidly produces a tall, branched flower stem. The leaves on the flowering stem are much more finely divided and feathery than the broad, lobed basal leaves, and these finer leaves wilt and curl more visibly in warm conditions. The transition from broad leaf production to feathery bolt-stage leaves can appear almost overnight in hot summer weather.

What to do

• Sow a pinch of coriander seeds every 3 to 4 weeks from March to September rather than in a single large sowing. Each successive sowing provides a fresh supply of young, broad-leaved coriander as the previous sowing bolts.
• Sow direct rather than transplanting: coriander has a long taproot and strongly dislikes root disturbance. Transplanting from pot to bed dramatically accelerates bolting.
• Choose slow-bolt varieties: 'Leisure', 'Confetti', and 'Calypso' are significantly more bolt-resistant than unnamed coriander seed. In midsummer, even slow-bolt varieties will eventually bolt, but they give substantially longer to harvest.
• Grow coriander in a position with afternoon shade in summer: heat and direct sun are the primary bolting triggers. North-facing and east-facing positions, or the shade of a taller plant, extend the leaf-producing season considerably.

Aphids

Carrot-willow aphid (Cavariella aegopodii) and related species attack coriander and other plants in the carrot family, clustering at the growing tips and causing the young, emerging leaves to curl around the feeding colonies. In heavy infestations, the growing tip is completely distorted. Aphid feeding also transmits viruses that cause mosaic patterns and further leaf distortion.

What to do

• Inspect coriander growing tips weekly from May for aphid colonies. Small colonies can be squashed by hand or removed with a jet of water. Apply insecticidal soap spray to larger infestations, covering the growing tip and leaf undersides thoroughly.
• On coriander grown for leaf harvest, remove and replace severely aphid-infested plants: a new direct sowing takes only 3 to 4 weeks to reach harvest stage, which is faster than clearing a severe infestation.

Drought

Drought causes coriander leaves to wilt and curl and significantly accelerates bolting. Coriander in dry soil bolts within days of germination in hot summer weather. Consistent moisture is essential for keeping coriander in its leafy, vegetative stage rather than transitioning rapidly to flower production.

What to do

• Water coriander consistently: never allow the soil or compost to dry out completely. Water every 2 to 3 days in warm, dry conditions. In a pot or container, coriander may need daily watering in summer.
• Grow coriander in soil with plenty of incorporated compost to retain moisture. Avoid free-draining, sandy soils for summer coriander growing.

Leaf miner

Celery leaf miner (Euleia heraclei) occasionally attacks coriander and other plants in the carrot family. The larvae mine between the leaf surfaces, creating pale, blistered patches that cause the leaf to curl around the damaged areas. On coriander's relatively small, divided leaves, even minor mining damage is noticeable.

What to do

• Remove and destroy mined leaves promptly. On coriander grown for leaf harvest, the plant produces new growth from its base quickly; removing affected leaves at the stem rather than the leaf is more effective.

Powdery mildew

Powdery mildew on coriander produces white, powdery patches on the leaves, particularly in hot, dry conditions with cool nights. Affected leaves curl and yellow. Powdery mildew is more common on coriander in late summer when temperature fluctuations between day and night are greatest.

What to do

• Remove and destroy affected leaves. Improve airflow around densely planted coriander. Water at the base of plants rather than overhead. On a severely mildewed plant in late summer that is also beginning to bolt, it is often more practical to remove the plant and start a fresh sowing.

Frequently asked questions

Why are my coriander leaves curling?

Coriander leaves curl most often as a result of bolting (the plant running to seed), aphid feeding, or drought. When coriander bolts, the leaf shape changes dramatically: the lower, broad-lobed leaves are replaced by finely divided, feathery leaves on tall stems as the plant transitions from leaf production to flower and seed production. These feathery, bolt-stage leaves often appear to curl or shrivel in hot, dry conditions. Aphids colonise coriander growing tips and cause the young leaves to curl inward. Drought causes all the leaves to wilt and curl, and significantly accelerates bolting.

How do I stop coriander bolting?

Coriander is one of the most bolt-prone herbs in the UK garden, particularly in warm weather. To extend the leaf-producing season: sow little and often (a pinch of seeds every 3 to 4 weeks) rather than relying on a single large sowing; keep plants consistently watered and never let the soil dry out; grow in a position with afternoon shade in summer, as full sun and heat are the primary bolting triggers; choose slow-bolt varieties such as 'Leisure', 'Confetti', or 'Calypso' for summer growing; and harvest leaves regularly from the base to slow the plant's transition to the flowering stage. The best-quality coriander in the UK comes from March to May and August to October sowings; midsummer sowings in full sun bolt almost immediately.

Can I eat coriander flowers and seeds?

Yes. All parts of the coriander plant are edible. The white flowers are delicate and have a mild coriander flavour; they can be used as a garnish on salads and Asian dishes. The green, unripe seeds have a fresh, citrusy, intense coriander flavour that is excellent in chutneys, salads, and as a topping for bread. The fully ripe, dried seeds are the familiar spice used in curries, soups, and spice blends worldwide. If coriander bolts in your garden, allow it to flower and set seed: both are useful in the kitchen and the dried seeds can be saved for next season's sowing.

Why does my coriander die after a few weeks?

Coriander dies back quickly for two main reasons: bolting and root disturbance. Coriander is an annual that completes its life cycle (germinate, grow leaves, flower, set seed, die) very rapidly in warm conditions, sometimes in just 6 to 8 weeks in hot summer weather. Once it bolts and sets seed, the plant dies. The second common reason is that most supermarket coriander is grown in dense clumps from multiple seeds in a pot and was never intended to survive long-term: the roots are heavily congested and the plant bolts almost immediately on reaching a warm windowsill. For longer-lasting coriander, sow a pinch of seeds directly into a larger pot or garden bed every 3 to 4 weeks, thin to a single plant or small cluster, water consistently, and harvest regularly from the base.