Lychnis, covering plants from the scarlet Maltese cross (Lychnis chalcedonica) to the silver-leaved rose campion (Lychnis coronaria), is a robust and colourful perennial family. But leaf curling indicates one of several problems that need addressing. Powdery mildew is the most widespread issue and affects virtually all lychnis species by midsummer. Aphids, drought, rust, anther smut, and leaf spot each produce distinctive symptoms that help identify the right response.
1. Powdery mildew
Powdery mildew is the most prevalent disease of lychnis and affects the entire genus to some degree. The fungal mycelium colonises the leaf surface from midsummer onward, coating it in a white or pale grey powdery layer. As the infection spreads, leaf cells are weakened and the margins curl upward, the tissue between the veins puckers, and the leaves lose their fresh appearance entirely. Plants of Lychnis chalcedonica and Lychnis viscaria are particularly prone, and without intervention the mildew spreads rapidly through a clump in warm dry conditions.
What to look for
- White or pale grey powdery coating on upper and lower leaf surfaces
- Leaf margins curling upward and tissue puckering between the veins
- Leaves looking smaller and more congested than healthy growth
- Worst in warm dry summers with poor airflow between plants
- Spreading rapidly through a clump from midsummer onward
How to fix it
Cut the plant back hard to just above the crown immediately after the first flush of flowers. Remove all foliage, including the stem leaves below the affected tips, and dispose of it in the bin rather than composting. Water well and apply a balanced liquid feed. Lychnis responds vigorously to this treatment and usually produces a flush of clean new growth within two to three weeks. Divide crowded clumps every two to three years to improve airflow. Plant with 30 to 40 cm of space between plants rather than in tight groups. Water at the base only and in the morning.
2. Aphids
Aphids cluster at the growing tips of lychnis in spring and early summer, feeding on the sap of the softest new growth. Their saliva disrupts the normal development of leaf cells, and the result is a tightly coiled or cupped growing tip that fails to unfurl into the normal flat leaf. Because lychnis produces basal leaves and then sends up flowering stems relatively quickly, aphid damage at the tip can distort the leaves directly below the flower buds, making it very conspicuous during flowering.
What to look for
- Tightly coiled or cupped growing tips that fail to unfurl
- Small green, grey, or black aphids within the curled tissue
- Sticky honeydew on stems below the infestation
- Ants farming the colony on the flower stems
- Damage concentrated on new growth and flower stem leaves
How to fix it
Knock colonies off with a firm water jet or apply insecticidal soap directly to the colony. Removing the infested growing tip eliminates the colony and the worst of the distorted growth in one action. Encourage natural predators including ladybirds and hoverflies by maintaining diverse planting around the lychnis and avoiding broad-spectrum insecticide sprays. Subsequent growth after the aphids are removed will be undamaged, and the existing distorted leaves will not straighten but will be hidden beneath new healthy growth.
3. Drought stress
Lychnis, particularly Lychnis coronaria with its silver woolly leaves, is reasonably drought-tolerant but can still curl its leaves during extreme dry spells, especially on young plants that have not established deep roots. The leaves roll lengthwise as the plant reduces water loss through its surface. Lychnis chalcedonica and Lychnis flos-cuculi, which naturally grow in moister habitats, are more sensitive to drought and curl more readily than the drier-ground species.
What to look for
- Leaves rolling lengthwise along their midrib
- Soil dry below the surface near the plant
- Moister-habitat species affected before L. coronaria
- Recovery after deep watering within hours
- No pest, fungal coating, or spots to explain the curling
How to fix it
Water deeply and apply a mulch of bark chip or garden compost to retain moisture around moisture-loving species. Lychnis coronaria grown in the right well-drained sunny position rarely needs watering once established. Lychnis chalcedonica and other moister-habitat species benefit from a consistently moist but well-drained soil: improve clay soils with organic matter and improve sandy soils with compost before planting. Water young plants every three to four days for the first season until established.
4. Rust
Rust fungi can infect lychnis, producing orange or brown pustules on the underside of leaves and corresponding pale or yellow spots on the upper surface. The infected tissue curls and puckers around each pustule as the cells die. Rust is less common on lychnis than powdery mildew but can appear in seasons with alternating wet and dry spells, particularly on plants growing in humid spots with poor air circulation.
What to look for
- Orange, rust-coloured, or brown powdery pustules on the leaf underside
- Pale yellow spots or patches on the upper surface above each pustule
- Leaf tissue curling or puckering around affected areas
- Affected leaves yellowing and dropping prematurely
- Worse in humid conditions with alternating wet and dry weather
How to fix it
Remove and bin every leaf showing rust pustules as soon as they appear. Do not compost them: rust spores survive composting. Avoid overhead irrigation and water at the base only. Cutting the plant back entirely after flowering removes all infected material at once. A copper-based fungicide applied as a protective spray to uninfected leaves reduces further spread. Improving airflow by dividing congested clumps makes infection less likely in future seasons.
5. Anther smut
Anther smut (Microbotryum violaceum) is a fungal disease specific to the campion family that replaces the pollen-producing anthers with a mass of dark powdery spores. While the primary symptom is in the flowers rather than the leaves, infected plants often show associated leaf distortion, puckering, and curling. The disease is systemic: the fungal mycelium spreads through the whole plant and infected specimens cannot be cured. Bees and other flower visitors spread the spores between plants.
What to look for
- Dark dusty powder in the anthers of flowers instead of pollen
- Flowers distorted or reduced
- Leaves curling or puckering, particularly near the flowering stems
- Overall stunted or distorted look to the whole plant
- Other lychnis, silene, or related plants nearby may also be infected
How to fix it
Remove and destroy every infected plant as soon as you notice the characteristic dark dusty anthers. Bag the plant before removing it from the soil to prevent spores dispersing from the flowers. Do not compost infected material. Disinfect tools. Do not plant lychnis, silene, or related species in the same position for several seasons. Source replacement plants from reputable nurseries and inspect the flowers before planting near other campion-family plants.
6. Leaf spot
Fungal leaf spot diseases can affect lychnis, producing circular or irregular dark brown or black spots on the leaf surface. The tissue surrounding each spot often curls, yellows, or dies as the infection spreads. Leaf spot is most common in wet seasons or in closely spaced plantings where foliage stays wet for extended periods. It is rarely fatal but can reduce the ornamental quality of the plant significantly if left untreated.
What to look for
- Circular or irregular brown, black, or purple spots on the leaf surface
- Leaf tissue curling or dying around each spot
- Spots often with a darker border or a pale centre
- Worse in wet seasons or in plants with poor air circulation
- Lower and outer leaves affected first, spreading upward over time
How to fix it
Remove and bin every spotted leaf promptly. Avoid overhead watering: leaf spot fungi spread through water droplets splashing between leaves. Water at the base in the morning only. Cutting the plant back hard after flowering removes the majority of infected foliage at once and allows clean new growth to replace it. In wet seasons, a preventative copper-based fungicide spray on healthy leaves reduces spread. Dividing congested clumps to improve airflow and spacing plants further apart prevents conditions that favour the disease.
Quick diagnosis checklist
| What you see | Most likely cause | First action |
|---|---|---|
| White powder on leaves, margins curling up | Powdery mildew | Cut back hard after flowering, improve airflow |
| Growing tips coiled, aphids visible | Aphids | Water jet, insecticidal soap, remove infested tip |
| Leaves rolling lengthwise, soil dry | Drought | Water deeply, mulch, improve soil moisture |
| Orange pustules on underside, pale spots above | Rust | Remove infected leaves, cut back, copper spray |
| Dark dusty anthers in flowers, leaf distortion | Anther smut | Remove and destroy the whole plant |
| Brown or black spots on leaves, tissue curling around them | Leaf spot | Remove spotted leaves, water at base only |
Frequently asked questions
Why are my lychnis leaves curling?
The most common reason lychnis leaves curl is powdery mildew. The fungal infection creates a white coating on the leaf surface and causes margins to cup and curl, particularly from midsummer onward. Cut the plant back after flowering to remove infected growth and stimulate fresh foliage. Aphids on the growing tips cause a different type of curling affecting only the newest growth.
What is the white powder and curling on my lychnis?
White powder combined with leaf curling on lychnis is powdery mildew, a fungal infection that is very common on this genus. It thrives in warm dry conditions with poor air circulation. Remove badly affected leaves, cut the plant back after flowering, improve spacing, and water at the base rather than overhead. Most lychnis recover quickly with a post-flowering cutback.
Can anther smut affect lychnis leaves?
Anther smut (Microbotryum violaceum) primarily replaces the pollen in lychnis flowers with dark spores rather than causing leaf symptoms. However, infected plants often show some leaf distortion alongside the flower symptoms. If you notice dark dusty anthers in the flowers combined with leaf problems, remove and destroy the entire plant to prevent the spores spreading to neighbouring campions and related plants.
Should I cut back lychnis when the leaves curl?
Yes. Cutting lychnis back to within a few centimetres of the crown after the first flush of flowers removes mildewed or aphid-damaged foliage and encourages a second flush of clean growth and often a repeat of flowers. Water and apply a liquid feed after cutting back. This is the single most effective intervention for improving the appearance of a lychnis with curling leaves.