Aquilegia, or columbine, is one of the most reliably self-sufficient plants in a UK cottage garden. Aquilegia vulgaris and its hybrids, including the tall McKana series with their large, bicoloured spurred flowers, flower freely in May and June, set seed without any help, and pop up in new spots around the border every year. They are genuinely almost indestructible. But in June and July, just as the flowers finish, the foliage often starts to look wrong: curling, shredding, covered in white powder, or simply wilting despite no obvious cause. The two most likely culprits are aquilegia sawfly larvae and powdery mildew, and both are reliably fixed with one simple action.
Aquilegia sawfly: the main cause of leaf curling and shredding
Aquilegia sawfly (Pristiphora aquilegiae) is the primary reason aquilegia leaves curl and shred in UK gardens. The adult sawfly is a small, inconspicuous flying insect that lays its eggs on the undersides of aquilegia leaves in late spring. The larvae hatch as pale green, caterpillar-like insects, typically around 12 to 15 millimetres long when fully grown, and immediately begin feeding on the foliage. They eat from the leaf edges inward or punch holes in the blade and work outward, and as they feed the damaged leaf tissue curls, dries, and collapses. A colony of larvae can strip a large aquilegia plant to bare stems within a week, leaving nothing but the skeleton of veins and a collection of shrivelled, curled leaf remnants.
The damage is most common from late May through July, timed almost exactly to coincide with the end of the flowering season. This timing is significant: the plant is already entering a natural post-flowering decline, and the sawfly damage accelerates that process dramatically. The larvae feed in small groups, often concentrated on a few stems before moving to the next. Checking the undersides of the most damaged leaves almost always reveals the larvae themselves, clinging to the midrib or huddled along the leaf margin. The pale green colour makes them easy to miss on first inspection, but once you know to look for them they are usually visible without difficulty.
Hand-picking is the most immediate and effective treatment. Go over the plant carefully, checking both surfaces of every leaf, and remove each larva you find. Drop them into soapy water or crush them. On a plant with a manageable number of stems this takes only a few minutes and removes the entire population in one session, provided you are thorough. Where infestations are heavy and hand-picking is not practical, pyrethrum spray applied directly to the larvae on the leaf undersides is effective and breaks down quickly in the environment. Avoid applying broad-spectrum insecticides to flowering plants or their immediate vicinity, as sawfly is a minor problem in the context of the garden ecosystem and the collateral damage to beneficial insects is significant.
The most effective preventive action is also the simplest. Cut aquilegia back hard to ground level in mid-June, once flowering is finished. This removes any eggs already on the foliage and breaks the larval lifecycle before the population can build. It also removes any larvae that have already hatched. The plant regenerates from the crown within two to three weeks, producing a flush of clean, fresh foliage that is far less susceptible to a second-generation attack because the new growth emerges later in the season as temperatures ease.
Powdery mildew: the post-flowering white coating
Powdery mildew, caused by the specialist fungus Erysiphe aquilegiae, is extremely common on aquilegia by midsummer and is the main reason plants start to look grey, dusty, and exhausted from July onwards. The disease produces a white or pale grey floury coating on the upper surfaces of the leaves and sometimes on the stems. Affected leaves curl, distort, and eventually yellow and drop. In a dry summer, the progression from the first powdery patches in late June to a plant entirely covered in white growth can happen within three to four weeks.
Aquilegia is naturally prone to powdery mildew because the conditions in which it thrives, dappled shade and well-drained soil at the edge of a border, overlap almost exactly with the conditions the fungus requires: warm days, cool evenings, dry soil, and limited air movement around the foliage. The post-flowering period intensifies the problem because the plant's resources are depleted after seed production and its natural resistance is lower. Plants in open, exposed positions tend to show mildew later and less severely than those in sheltered spots where air stagnates around the foliage.
The most reliable fix is hard cutting back. Remove all the foliage and stems to within a few centimetres of the ground in mid-June, before mildew has become established or immediately after you notice the first signs of white coating. The regrowth emerges clean. Attempting to spray an established mildew infection on aquilegia with potassium bicarbonate or other fungicides is rarely worthwhile because the post-flowering foliage is already in decline and the effort required to treat a densely leaved plant thoroughly is disproportionate to the benefit. Cutting back achieves the same result faster. In gardens where mildew appears very early, planting aquilegia in a more open position with better air movement, or choosing species with a reputation for mildew tolerance such as Aquilegia canadensis, can help in subsequent seasons. Avoiding high-nitrogen feeds reduces the production of the soft, mildew-susceptible growth that fertilised plants tend to put on.
Aphids on spring shoot tips
Before the sawfly arrives, aphids are the most common pest problem on aquilegia in spring. Small colonies of pale green or grey-green aphids establish on the young shoot tips and emerging flower stems from April onwards, feeding on the sap and causing the newest leaves to curl downward and inward. Sticky honeydew coats the foliage below the feeding sites, and a thin black sooty mould may develop on the most heavily infested plants. The damage is usually contained to the shoot tips and does not spread significantly as the season progresses, particularly once natural predators arrive in numbers from late April.
Treatment on established garden aquilegias is rarely necessary. Ladybird and lacewing larvae reduce aphid populations on most plants within a few weeks without any intervention. Where colonies are dense on a plant that is about to flower, rub the insects off by hand or knock them loose with a jet of water from a hose. Avoid using insecticide sprays on aquilegia when the flowers are open, as the plants are a significant source of nectar and pollen for bumblebees and long-tongued solitary bees.
Leaf miners and their distinctive tunnels
The aquilegia leaf miner (Phytomyza aquilegiae) is a small fly whose larvae feed between the upper and lower surfaces of aquilegia leaves, creating the pale, winding, serpentine tunnels that are the characteristic sign of their activity. Hold an affected leaf up to the light and the tunnel is immediately visible as a paler, translucent channel winding across the leaf blade. The tissue immediately surrounding the tunnel is slightly puckered and distorted, and in heavy infestations the leaf surface becomes blistered and irregular. The cosmetic effect on an individual leaf can be striking, but leaf miner rarely causes significant harm to aquilegia as a whole, and established plants tolerate even substantial leaf miner damage without any effect on flowering or vigour.
No treatment is needed in most cases. Remove the worst-affected leaves and discard them in the bin rather than the compost heap, which disposes of the larvae inside. Where a plant has leaf miner damage in the same season as sawfly or mildew, cutting the whole plant back in mid-June resolves all three problems simultaneously.
Vine weevil in containers
Aquilegia grown in containers, where vine weevil (Otiorhynchus sulcatus) grubs can cause significant root damage without any indication at soil level until the plant collapses. The adult vine weevil notches the leaf margins in a characteristic scalloped pattern during summer nights, but this alone rarely causes curling or wilting. The real damage comes from the white, C-shaped grubs in the compost, which feed on the roots through autumn and spring, cutting the plant off from water and nutrients. A container-grown aquilegia that wilts suddenly despite moist compost and was not previously under stress almost certainly has vine weevil grubs in the root zone.
Check container-grown aquilegia by sliding the plant out of its pot in early autumn. Inspect the compost for white grubs around the root ball and destroy any you find. Apply a nematode drench in early September while soil temperatures are still above 14 degrees Celsius, which is the threshold for effective nematode activity. Nematodes are available from most UK garden retailers and are the most reliable non-chemical treatment for vine weevil in container compost.
Downy mildew in cool, wet conditions
Downy mildew produces different symptoms to powdery mildew and is associated with cool, wet conditions rather than dry summer heat. The upper leaf surface develops pale yellow or brown patches, often angular and limited by the leaf veins. On the underside, a greyish-white or pale purple downy fungal growth is visible over these patches. Affected leaves may curl slightly at the margins and eventually brown and die. Downy mildew on aquilegia is less common than powdery mildew in most UK gardens but can be significant in a cool, wet spring.
Improve air circulation around plants by removing crowded stems and thinning dense plantings. Avoid overhead watering. Remove affected leaves promptly and dispose of them in the bin. Where downy mildew is persistent across several seasons, cutting back immediately after flowering, even before any symptoms appear, and reducing plant density in the border provides better long-term control than any spray programme.
Natural post-flowering decline: when nothing is wrong
It is worth noting that aquilegia foliage naturally looks tatty by midsummer even when no disease or pest is involved. After the flowers have finished and the seed pods have formed and dropped, the leaves lose their fresh green colour, yellow at the margins, and develop a generally wilted, past-it appearance. This is normal senescence, not a disease. Many gardeners mistake this natural decline for a problem and apply treatments that are not needed. The practical response is the same regardless: cut the plant back hard in mid-June and let the new foliage show whether any actual problem was present. If the fresh growth comes through clean and healthy, the earlier tattiness was simply normal post-flowering decline. If the new growth shows signs of mildew or sawfly within two to three weeks of emerging, you know what you are dealing with.
Prevention: what to do each year
Keeping aquilegia healthy through the season requires very little effort if you build two simple habits. From early May, inspect the undersides of the leaves weekly for sawfly eggs and newly hatched larvae. The eggs are laid singly or in small groups along the leaf veins and are pale and oval. Removing leaves with eggs on them before the larvae hatch is the most efficient form of control. Once larvae are present, hand-pick them promptly before they can build into a population large enough to cause rapid defoliation.
In mid-June, cut everything back to ground level. Do this as soon as the last flowers have finished, allowing a few seed pods to ripen and drop first if you want self-seeded plants for the following year. The cut-back removes any remaining sawfly larvae, all mildew-affected foliage, and any leaf miner damage in a single action and prompts the flush of clean regrowth that carries the plant through to autumn in good condition. Aquilegia is one of those plants where a hard post-flowering cut genuinely transforms its contribution to the garden for the rest of the season. Plants that are left uncut are typically grey, mildewed, and threadbare by August. Plants that are cut back in mid-June are producing fresh, attractive foliage by July.
In positions that are prone to mildew, partial shade rather than deep shade reduces the combination of warm dry air and sheltered stillness that mildew favours. Avoid feeding aquilegia with nitrogen-heavy fertilisers, which produce soft, rapidly growing foliage that is significantly more susceptible to both mildew and aphid attack than the harder growth that plants in moderately fertile, unfed borders produce. Aquilegia self-seeds freely, which means that even if individual plants are short-lived, the colony perpetuates itself without any effort on your part. Allowing a proportion of seed pods to ripen and drop before cutting back guarantees a new generation of seedlings in the surrounding soil within a few months.
Frequently asked questions
Why are my aquilegia leaves curling?
In UK gardens, aquilegia sawfly larvae (Pristiphora aquilegiae) are the most common cause of leaf curling on columbine from late May through July. The pale green larvae feed from the leaf edges inward and cause the foliage to curl, shred, and eventually collapse. Powdery mildew is the other main culprit, producing a white floury coating and leaf distortion after flowering in dry summers. Aphids on spring shoot tips and leaf miners creating pale winding tunnels are less common but worth ruling out.
What does aquilegia sawfly look like?
Aquilegia sawfly larvae are pale green and caterpillar-like, typically around 12 to 15 millimetres long when fully grown. They feed in small groups on the undersides and edges of the leaves, eating outward from the leaf margin or from holes punched in the blade. A plant can be stripped to bare stems within a week if a large batch of larvae is present. The adult sawfly is a small, inconspicuous flying insect that lays eggs on the leaf undersides in late spring.
Should I cut my aquilegia back after flowering?
Yes. Cutting aquilegia back hard to ground level in mid-June, once flowering is finished, is one of the most effective things you can do to manage both sawfly and powdery mildew. It removes the existing larval population and mildew-affected foliage in one action and prompts a flush of fresh, clean leaves. The plant rebounds quickly and the new growth is far less susceptible to mildew because it emerges as summer conditions ease. Allow a few plants to set seed first if you want self-seeded replacements.
Can aquilegia recover from sawfly damage?
Yes. Although a heavy sawfly infestation can strip an aquilegia to bare stems rapidly, the plant almost always recovers. Cut the plant back hard and it will push new growth from the crown within two to three weeks. Aquilegia is a tough, short-lived perennial that regenerates readily, and established plants tolerate severe defoliation without lasting harm. The risk of losing a plant to sawfly is low; the greater concern is allowing larvae to complete their lifecycle and build a larger population for the following season.
Why does my aquilegia look exhausted and white by midsummer?
This is very common and almost always powdery mildew. Aquilegia naturally declines after its May and June flowering period and the foliage often looks tatty by July regardless of disease, but in dry summers the combination of post-flowering exhaustion and powdery mildew produces plants that are grey-white, distorted, and almost entirely covered in fungal growth. The fix is simple: cut the whole plant back to ground level in mid-June. Fresh foliage regrows within two to three weeks and the new growth is typically clean and healthy through the rest of the summer.