Why are my cyclamen leaves curling?

Cyclamen leaves curl most commonly due to overwatering, heat stress, or cyclamen mite infestation. Overwatering is the single most common cause of cyclamen failure indoors: cyclamen grow from a flattened tuber that rots quickly when kept in waterlogged soil, and the resulting root and tuber damage causes the leaves to curl, yellow, and collapse; watering into the center of the plant or letting water sit on the tuber is particularly harmful. Heat stress causes cyclamen leaves to curl and the plant to yellow and go dormant when temperatures rise above 65 degrees Fahrenheit for extended periods; cyclamen are cool-weather plants that perform best at 50 to 65 degrees Fahrenheit and decline rapidly in warm indoor conditions. Cyclamen mites (Phytonemus pallidus) are microscopic arachnids that cause the youngest leaves to curl tightly inward and become distorted and brittle; they are invisible without a hand lens and concentrate in the youngest growth. Vine weevil grubs feed on the roots and tuber from below ground, causing sudden wilting and collapse even when watering seems correct. Gray mold (Botrytis cinerea) in humid, still conditions causes the leaves and flowers to rot and collapse.

Why are my cyclamen leaves curling and turning yellow?

Cyclamen leaves curling alongside yellowing most commonly indicate overwatering, heat stress, or the natural approach of summer dormancy. Cyclamen persicum (the florist cyclamen) is a cool-season plant that naturally yellows and goes dormant as temperatures rise in spring; this is normal behavior and not a problem. Overwatering in cool conditions causes yellowing and curl before the plant goes dormant: check the soil and allow it to dry between waterings. Heat stress above 65 degrees Fahrenheit accelerates the decline toward dormancy and can cause premature yellowing at any time of year indoors if the plant is near a heat source, in direct sun through a warm window, or in a centrally heated room. Move cyclamen to a cool, bright position (ideally 50 to 60 degrees Fahrenheit) such as an unheated but frost-free room, a north-facing windowsill, or a greenhouse in winter. For summer dormancy, reduce watering gradually as the leaves yellow and allow the plant to go dry; store the tuber dry in its pot in a cool, dark location and resume watering in autumn to restart growth. Cyclamen held too warm over summer often fail to rebloom because the heat prevents the flower bud initiation that requires cool temperatures.

What are cyclamen mites and how do I treat them?

Cyclamen mites (Phytonemus pallidus) are microscopic arachnids (about 0.2 mm) that are invisible to the naked eye but cause highly distinctive damage: the youngest leaves at the center of the plant curl tightly inward and become distorted, hardened, and often take on a bronze or silver color; flower buds may be distorted or fail to open. Unlike spider mites, cyclamen mites do not produce webbing. They are closely related to broad mites and cause similar damage by injecting toxic saliva into the tender growing tissue that disrupts normal cell development. Cyclamen mites thrive in high humidity and spread through plant-to-plant contact or on hands and tools. They are one of the most difficult plant pests to control. Treatment options include wettable sulfur applied to all leaf surfaces and the growing center of the plant, or abamectin (Avid), which is highly effective; repeat every 5 to 7 days for 3 applications. The tight curl of the center leaves makes it difficult for sprays to penetrate fully, so thorough coverage of the plant center is important. Isolate affected plants immediately to prevent spread to nearby cyclamen or other susceptible plants such as begonias, strawberries, and fuchsias. Heavily infested plants with multiple distorted growing points are difficult to recover and may be best discarded.

Cyclamen Leaves Curling — Why It Happens and How to Fix It

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At a glance

Leaves yellowing and curling with wet soil or rotting tuber: Overwatering or tuber rot; reduce watering and improve drainage
Plant wilting suddenly despite correct watering, no visible pests: Vine weevil grubs; unpot and inspect roots and tuber
Leaves curling and plant yellowing in warm conditions: Heat stress or summer dormancy; move to cool location
Youngest center leaves curling tightly and becoming distorted: Cyclamen mites; treat with wettable sulfur or abamectin
Leaves and flowers collapsing with gray fuzzy mold in humid conditions: Gray mold (Botrytis); improve air circulation and remove affected tissue

Why cyclamen leaves curl

Cyclamen (Cyclamen persicum hybrids for indoor use; Cyclamen hederifolium and related species for outdoor use) are cool-season plants grown for their swept-back flowers and attractive marbled foliage in autumn and winter. They are among the most popular gift and holiday plants but have a reputation for being difficult indoors because their requirements are often misunderstood. The two most critical facts about cyclamen care are that they prefer cool temperatures (below 65 degrees Fahrenheit) and that their flat tubers rot easily from overwatering. Most cyclamen problems trace back to one of these two causes.

Cause 1: Overwatering and tuber rot

Signs: The leaves are yellowing, wilting, and curling despite regular watering. The soil is consistently moist or wet. The plant looks increasingly unhealthy despite apparent care. Removing the pot may reveal brown, soft, or mushy areas on the flat tuber. Stems at the base may be collapsing. The tuber may smell unpleasant if Erwinia bacterial soft rot is involved.

Why it happens: Cyclamen tubers evolved in seasonally dry Mediterranean climates and are susceptible to rot when kept in persistently wet soil. The common practice of watering the center of the plant compounds this problem by keeping moisture in contact with the top of the tuber, which is where rot most often begins. In heavy potting mix or in pots without adequate drainage, overwatering rapidly causes root and tuber rot that prevents the plant from taking up water even from wet soil.

Fix: Water cyclamen from below by placing the pot in a shallow tray of water for 20 to 30 minutes, then removing it and allowing the excess to drain; never leave the pot sitting in water. Alternatively, water carefully at the soil surface, avoiding the tuber and stem bases. Allow the top of the soil to dry before watering again. Repot into well-draining compost if the current medium is heavy. If tuber rot is present, remove all rotted tissue, dust the cut surfaces with sulfur powder or cinnamon, and allow to dry before replanting in fresh compost.

Cause 2: Vine weevil grubs

Signs: The plant wilts and collapses suddenly despite apparently correct watering and cool conditions. No visible pests are present on the leaves. Removing the plant from the pot reveals cream-colored, C-shaped grubs (the larvae of Otiorhynchus sulcatus) feeding on the roots and tuber. The tuber may be extensively hollowed out. Notched leaf edges may indicate adult vine weevil feeding at night.

Why it happens: Vine weevil is one of the most destructive pests of container plants in cool climates. The adult beetles lay eggs in the soil during summer, and the grubs hatch and feed on roots and tubers through autumn and winter, causing the sudden collapse that is discovered when the plant fails to recover from what looks like drought stress. Cyclamen tubers are particularly attractive to vine weevil grubs. The adults feed on leaf edges at night but cause less damage than the root-eating grubs.

Fix: Unpot the plant and inspect the root ball for grubs; pick out and destroy all grubs found. Apply beneficial nematodes (Steinernema kraussei or Heterorhabditis bacteriophora) as a soil drench in late summer to kill grubs before they damage the tuber; this is the most effective biological control. Imidacloprid applied as a preventive soil drench at potting time provides chemical protection for the season. Check newly purchased cyclamen for adult weevil notching on the leaf edges before bringing them indoors.

Cause 3: Heat stress and summer dormancy

Signs: The leaves are curling, yellowing, and the plant appears to be declining. The conditions are warm (above 65 degrees Fahrenheit). The decline is gradual and affects the whole plant. The plant may be near a radiator, in a heated room, or in a sun-facing window in late spring. This may be the natural summer dormancy cycle rather than a problem.

Why it happens: Cyclamen persicum is a cool-season plant that actively grows and flowers from autumn through spring in cool conditions, then naturally goes dormant as temperatures warm. Temperatures above 65 degrees Fahrenheit accelerate this decline and can cause the plant to yellow and die back prematurely. Centrally heated homes in winter are often too warm for cyclamen to thrive, which is why they perform better in cool rooms, unheated conservatories, or on cool windowsills away from radiators.

Fix: Move cyclamen to the coolest position available: a north- or east-facing windowsill, an unheated spare room, or a cool conservatory. The ideal temperature range is 50 to 60 degrees Fahrenheit at night and no more than 65 degrees Fahrenheit during the day. If the plant is entering summer dormancy naturally, reduce watering gradually and allow it to go dry; store the pot on its side in a cool, dark location through summer and resume watering in late summer to restart autumn growth.

Cause 4: Cyclamen mites

Signs: The youngest leaves at the center of the plant are curling tightly inward and becoming distorted, thickened, and sometimes bronzed or silvery. Flower buds in the center of the plant may be twisted or fail to develop normally. The damage is concentrated on the newest growth and worsens as more leaves emerge. No webbing is present (distinguishing this from spider mites). The mites themselves are invisible without a hand lens.

Why it happens: Cyclamen mites (Phytonemus pallidus) thrive in the cool, humid conditions that cyclamen prefer, which distinguishes them from spider mites that prefer hot, dry conditions. They spread through plant-to-plant contact and on hands and tools. Nurseries and garden centers occasionally sell infested plants, and cyclamen mites can spread rapidly through a collection once introduced.

Fix: Isolate affected plants immediately. Apply wettable sulfur or abamectin (Avid) to all leaf surfaces, concentrating on the center of the plant where mites are densest; repeat every 5 to 7 days for 3 applications. Disinfect hands and tools after handling affected plants. Heavily infested plants with severely distorted centers are difficult to recover and may be best disposed of to prevent spread.

Cause 5: Gray mold (Botrytis)

Signs: Flowers, leaves, and stems are collapsing and developing a gray, fuzzy mold coating. The collapse typically starts on dead or dying tissue (spent flowers, yellowing leaves) and spreads to living tissue in humid conditions. The problem is most severe when cyclamen are kept in still, humid air. Removing spent flowers and yellow leaves promptly reduces the disease's ability to spread.

Why it happens: Gray mold (Botrytis cinerea) is a ubiquitous fungal pathogen that colonizes dying and damaged plant tissue in cool, humid, still air. Cyclamen are susceptible because they are grown in cool conditions that also favor Botrytis. Overhead watering that wets the flowers and foliage, poor air circulation around dense plantings, and failure to remove spent flowers and yellow leaves all promote gray mold development.

Fix: Remove and dispose of all affected flowers, buds, and leaves promptly. Improve air circulation by spacing plants and avoiding enclosed, still conditions. Water from below to keep the foliage dry. Apply a copper-based fungicide or a product containing fludioxonil preventively in high-risk conditions. Reduce humidity around the plants where possible.

Cyclamen Leaves Curling