Pulmonaria, or lungwort, is one of the most valuable spring perennials for shade gardens. Its attractively spotted or silver-washed leaves emerge early in the season alongside clusters of blue, pink, or white funnel-shaped flowers, and with proper care the foliage remains ornamental well into autumn. The plant has one significant weakness: it is very prone to powdery mildew in summer, particularly if the soil dries out. Understanding this tendency and knowing the simple management steps that prevent or reset it makes all the difference between pulmonaria that looks good year-round and one that deteriorates to a pile of curled, white-dusted leaves by August.
1. Powdery mildew
Powdery mildew is the defining summer problem of pulmonaria and affects most plants not managed proactively. The fungal pathogen thrives when warm, dry air meets the large hairy leaves, which hold humidity close to their surface. The mildew colonizes leaf surfaces and causes a white to grey powdery coating, alongside upward curling and yellowing of infected leaves. Drought stress dramatically accelerates the process: plants that dry out even once in summer are almost certain to develop severe mildew within days. Species pulmonaria and older cultivars are generally most susceptible; many newer varieties have been bred with improved resistance.
What to look for
- White or grey powdery coating on upper leaf surfaces
- Leaves curling upward and inward around infected areas
- Rapid deterioration following any period of drought stress
- Infection spreading from the oldest leaves outward
- New basal shoots at the crown remaining clean while older leaves deteriorate
How to fix it
Cut the entire plant back hard to ground level as soon as the flowers fade in late spring. This is the single most effective step: it removes all infected or at-risk growth and stimulates a fresh rosette of clean, healthy leaves that will remain ornamental through summer and into autumn. Water and mulch thoroughly after cutting back. Apply a sulfur-based or potassium bicarbonate fungicide if mildew is spreading before you can cut back. Choose mildew-resistant cultivars such as 'Sissinghurst White', 'Diana Clare', or 'Opal' for problem sites.
2. Drought stress
Pulmonaria evolved in moist woodland and is genuinely intolerant of drought. Even a few days of soil dryness in summer can trigger both leaf curl and the onset of powdery mildew. The large, hairy leaves have a high transpiration rate that quickly exhausts available soil moisture in warm weather, particularly in positions that receive more than a few hours of direct sun. Container-grown pulmonaria and plants in shallow soils over chalk are most vulnerable.
What to look for
- Leaves rolling inward and looking wilted or dull
- Soil dry at depth when probed
- Hairy leaf surface feeling dry and slightly rough rather than cool and moist
- Powdery mildew appearing shortly after drought symptoms
- Leaves recovering partially after deep watering
How to fix it
Water deeply and consistently at the base of the plant to keep the root zone moist throughout summer. Apply a generous layer of organic mulch, 5 to 8 cm deep, to retain moisture and regulate soil temperature. Position pulmonaria where it receives morning light and afternoon shade at most. On very free-draining soils, incorporate large amounts of organic matter before planting. After the post-flowering cut back, water well to support the new growth flush.
3. Slugs and snails
Slugs are one of the most persistent pests of pulmonaria. They are attracted to the large, fleshy leaves and feed on both the hairy leaf surface and the leaf edges. Damaged areas curl and deteriorate. Because pulmonaria grows in moist, shaded positions that slugs prefer, and because it produces large, succulent leaves, it is particularly vulnerable. Spring growth and the new flush of leaves after the post-flowering cut back are both high-risk periods.
What to look for
- Irregular holes in leaf surfaces with ragged edges
- Leaf edges eaten and curling around damage sites
- Silvery slime trails on leaves, stems, and nearby soil
- Damage appearing overnight or after rain
- New growth targeted immediately after the post-flowering cut back
How to fix it
Apply iron phosphate slug pellets around the plant in early spring and again after the post-flowering cut back. Use copper tape barriers around container pulmonaria. Check under the plant and nearby mulch at night with a torch and remove slugs by hand. Avoid over-mulching directly around the crown. Encourage ground beetle, frog, and hedgehog populations as effective natural slug controls.
4. Vine weevil
Vine weevil is a significant pest of pulmonaria, particularly container-grown specimens. Adult weevils cut U-shaped notches in leaf margins at night. The larvae eat roots underground from late summer through winter, causing the above-ground plant to wilt, curl, and eventually collapse as if drought-stressed despite the soil being moist. Container pulmonaria is at higher risk than garden plants because the confined root zone is quickly overwhelmed by even a small grub population.
What to look for
- U-shaped notches cut into leaf margins (adult feeding)
- Plants wilting and curling despite moist soil in late summer and autumn
- Crown loose and plant rocking easily in its pot or in the ground
- White, legless, C-shaped grubs with a brown head in the soil around roots
- Adults found under pots and debris at night
How to fix it
Apply biological control nematodes (Steinernema kraussei) to moist soil in late summer when soil temperature is above 5 C. For container pulmonaria, repot each spring into fresh compost and check carefully for grubs. Remove adult weevils by torchlight at night. A systemic insecticide drench is a chemical option where permitted for severe infestations.
5. Leaf spot
The natural spotting on pulmonaria leaves (which is part of their ornamental appeal) can make it harder to spot disease-induced leaf spot. Fungal leaf spot diseases produce darker, water-soaked or dry lesions that differ from the natural pale silver or white spots of healthy pulmonaria leaves. Affected tissue may curl and crisp around lesions. Leaf spot is most common in wet summers or on plants receiving overhead irrigation.
What to look for
- Dark brown, black, or water-soaked spots distinct from the natural silver spotting
- Lesions enlarging and merging in wet conditions
- Leaf tissue curling and crisping around badly affected spots
- Spots lacking the clean, pale color of natural pulmonaria markings
- Infection spreading from older leaves upward
How to fix it
Remove and dispose of infected leaves. Avoid overhead watering. Apply a copper-based fungicide every ten to fourteen days. The post-flowering cut back removes all infected leaves and gives the plant a clean restart. In wet seasons, this cutback is especially important.
6. Root rot
While pulmonaria needs consistently moist soil, it does not tolerate compacted or waterlogged conditions. In heavy clay soils or pots without drainage, root rot causes leaves to yellow, curl, and collapse despite the soil being wet. The contradiction is similar to drought: the plant cannot access water because its root system has been destroyed by anaerobic conditions and fungal pathogens.
What to look for
- Leaves curling and yellowing despite wet soil
- Plant wilting progressively and not recovering
- Crown soft or foul-smelling at soil level
- Root system brown and mushy rather than white and firm
- Plant declining through winter or spring in waterlogged conditions
How to fix it
Improve drainage by working coarse grit into planting soil. Plant pulmonaria in raised beds in gardens with persistent waterlogging. For containers, ensure drainage holes are open and pots do not sit in water-filled saucers. Pulmonaria needs moisture-retentive but well-structured, freely draining soil, not compacted or continuously saturated ground.
Quick diagnosis checklist
| Symptom | Most likely cause | First action |
|---|---|---|
| White powder, upward curl, summer deterioration | Powdery mildew | Cut back hard immediately after flowering |
| Inward roll, dry soil, precedes mildew | Drought stress | Deep water, mulch, shade position |
| Ragged holes, slime trails, overnight damage | Slugs and snails | Iron phosphate pellets, hand pick at night |
| Notched margins, wilt in moist soil, grubs at roots | Vine weevil | Nematode drench late summer |
| Dark spots distinct from natural silver markings | Leaf spot | Remove leaves, copper fungicide |
| Yellowing curl, wet soil, crown soft | Root rot | Improve drainage, replant |
Frequently asked questions
Why are my pulmonaria leaves curling?
Pulmonaria leaves most often curl because of powdery mildew infection in summer when the plant dries out, or drought stress causing the large spotted leaves to roll inward. Both are extremely common on lungwort. Cutting the plant back hard after flowering prevents both problems by generating fresh, mildew-free growth.
Does pulmonaria always get powdery mildew?
Pulmonaria is very susceptible to powdery mildew in summer, especially if the soil dries out. However, many modern cultivars have been bred for improved mildew resistance. Cutting the plant back hard to basal level after flowering, mulching the root zone, and choosing resistant varieties like 'Sissinghurst White' or 'Diana Clare' all help prevent the problem.
Should I cut back pulmonaria when the leaves curl?
Yes. Cutting pulmonaria back hard to basal level as soon as the flowers fade is the single most effective management step. This removes any early mildew-infected growth, prevents the summer drought cycle that triggers mildew, and stimulates the plant to produce a fresh rosette of its attractively spotted leaves that looks good from midsummer into autumn.
Can pulmonaria grow in full sun?
Pulmonaria prefers shade to partial shade and struggles in full sun, where it is much more prone to drought stress and powdery mildew. In a sunny position, the leaves curl and scorch in summer and mildew arrives earlier. Move pulmonaria to a shadier spot if sun exposure is causing recurring problems.
What causes pulmonaria leaves to curl and go silver?
If pulmonaria leaves are curling and the surface appears silvery or stippled rather than spotted, the cause is likely vine weevil damage to roots (causing drought-like curl) or thrips feeding on leaf surfaces (causing silvery flecking alongside curl). Check for white grubs in the soil around the roots and for tiny insects on leaf undersides.