Why Are My Gomphrena Leaves Curling?

Aphid infestation

Aphids are the most common pest on gomphrena. They colonise the shoot tips and the undersides of the elliptical leaves, causing the leaves to curl and the developing flower buds to distort. Cotton aphid and green peach aphid are both found on globe amaranth. Heavy aphid pressure on young plants delays the production of flower heads, which gomphrena is slow to produce anyway given its long growing season requirement in the UK.

What to do

• Check the shoot tips and the undersides of young leaves regularly from early summer onwards.
• Spray with insecticidal soap every four to five days for two to three weeks, covering the undersides of leaves and shoot tips.
• A strong jet of water dislodges aphids from the robust, slightly hairy leaves effectively as a first step before chemical treatment.
• Avoid excess nitrogen feeding which produces lush soft growth particularly attractive to aphids.

Cold stress

Cold stress is one of the most common reasons gomphrena underperforms or looks sickly in UK gardens. As a tropical annual, gomphrena requires sustained warmth to grow and flower well: temperatures below 10 degrees Celsius at night cause the elliptical leaves to curl, pale, and develop a bleached or yellowed appearance. Plants put out too early after the last frost, or growing through a cold, wet UK summer, may look weak and stunted for weeks before conditions improve. In cool summers, gomphrena in a polytunnel or greenhouse consistently outperforms outdoor plants.

What to do

• Do not plant gomphrena outside until late May or early June when nighttime temperatures are reliably above 12 degrees Celsius.
• Harden off thoroughly for at least two weeks before planting out.
• Choose the warmest, most sheltered, sunniest position available. South-facing beds against a wall are ideal.
• Cover with fleece on unexpectedly cold nights in early summer. Cold-stressed plants usually recover once temperatures improve.

Drought stress

Gomphrena is more drought tolerant than many summer annuals but still requires consistent moisture to grow and flower well. In containers or in very free-draining soil during dry spells, the elliptical leaves curl inward and the plant's growth stalls. Drought-stressed gomphrena produces fewer and smaller flower heads. Once watered, the plant recovers well, but repeated drought cycles shorten the productive cutting season significantly.

What to do

• Water gomphrena regularly during dry spells, particularly from midsummer when the plants are actively producing flower heads.
• Container-grown gomphrena needs watering every two to three days in warm weather. Check the compost daily and water before the leaves show curl.
• Mulch around border plants to retain soil moisture and reduce watering frequency.

Overwatering

While gomphrena benefits from regular moisture, it does not tolerate persistently waterlogged conditions. In containers without adequate drainage or in heavy clay soil during a wet UK summer, the roots deteriorate and the plant declines. The leaves yellow and curl even when the compost is wet, and the stems may become soft at the base. Overwatering is most likely during cool, cloudy periods when the compost dries much more slowly than in warm, sunny weather.

What to do

• Plant gomphrena in well-drained soil or use a free-draining container compost blended with perlite.
• Ensure containers have adequate drainage holes and reduce watering frequency during cool or overcast periods.
• Allow the surface of the compost to dry between waterings rather than keeping it consistently moist.

Spider mite

Spider mite occasionally affects gomphrena in hot, dry conditions, particularly under glass or in very sheltered outdoor positions. The slightly hairy leaves develop fine bronzing or stippling on the upper surface and the leaf edges curl. Fine webbing appears between the stems in more severe cases. The warm conditions that gomphrena prefers are also ideal for spider mite development, so the two can coincide, particularly in a hot, dry summer.

What to do

• Examine the undersides of curling leaves for the tiny mites, their eggs, and characteristic fine webbing.
• Spray with insecticidal soap or neem oil every five to seven days for four to six weeks.
• Increase humidity by misting the foliage: spider mites are inhibited by moist conditions.
• For plants under glass, the predatory mite Phytoseiulus persimilis provides highly effective biological control.

Frequently asked questions

Why are my gomphrena leaves curling?

Gomphrena leaves curl most often from aphid infestation or cold stress. Aphids colonise the shoot tips and the undersides of the elliptical leaves, causing them to curl and distort. Cold nights below 10 degrees Celsius cause the large leaves to curl, pale, and look bleached, as gomphrena is a warm-season tropical annual that performs poorly in cool conditions.

Why are my globe amaranth leaves going yellow?

Yellow leaves on gomphrena most often indicate overwatering, cold stress, or iron deficiency in very alkaline soil. Check the compost moisture: if it is persistently wet, reduce watering and ensure better drainage. Cold temperatures below 10 degrees also cause yellowing and curling of the leaves. In very alkaline conditions, apply a chelated iron feed to correct chlorosis.

How do I dry gomphrena flowers?

Cut gomphrena stems when the clover-like flower heads are fully coloured but before they begin to show any browning. Remove the lower leaves and hang in small bunches upside down in a warm, dry, well-ventilated space away from direct sunlight. Drying takes one to two weeks. The papery flower heads hold their vibrant colour excellently and last for months or years in dried arrangements.

When should I sow gomphrena?

Sow gomphrena under glass in March or April at 20 to 22 degrees Celsius. Soak the seeds in warm water for 24 hours before sowing to improve germination, which can otherwise be slow and erratic. Plant out after the last frost in late May or early June in a warm, sunny position. Gomphrena needs a long growing season to flower well in the UK.