Hemerocallis Leaves Curling

Daylily rust

Daylily rust (Phakopsora hemerocallidis) is the most distinctive cause of leaf problems on hemerocallis and one of the more serious fungal diseases affecting the genus. The infection begins as small, pale yellow or greenish spots on the upper leaf surface. Turn the leaf over and you will find corresponding raised, powdery orange pustules at each spot. As rust spreads, the leaf curls and yellows outward from each affected area, and severely infected leaves die back from the tips. The orange spore powder rubs off easily on your fingers, providing immediate confirmation. Rust spreads rapidly by airborne spores and can move through a daylily collection quickly in warm, humid weather.

Remove and bin all affected leaves immediately. Do not compost infected material. Apply a fungicide containing myclobutanil, trifloxystrobin, or sulphur to all remaining foliage, including the undersides of leaves where pustules form, and repeat every ten to fourteen days through the growing season. Improve air circulation around plants by spacing clumps at least 45 cm apart and removing surrounding weeds and debris. Some hemerocallis cultivars show better rust resistance than others: evergreen daylily types tend to be more susceptible than deciduous forms. In gardens where rust recurs annually, preventive fungicide applications beginning in early summer are more effective than reactive treatment.

Thrips

Thrips are tiny, slender insects that feed by rasping the surface of daylily leaves and flower buds. Infested leaves develop a distinctive silver or bronze streaking running along their length, and the leaf tissue curls and twists as the feeding damage disrupts normal growth. Flower buds may fail to open or produce distorted, scarred blooms. Thrips feed inside the tightly rolled emerging leaves and in the base of the plant where the foliage emerges from the crown, making them difficult to see without carefully unrolling affected tissue. Their narrow, pale bodies are only about 1 mm long but visible on a white surface if you tap a leaf over paper.

Thrips control requires persistence because the insects hide deep in leaf bases and in flower buds where sprays struggle to reach. Remove and bin the most heavily affected leaves. Apply an insecticide specifically labelled for thrips to the crown area and the bases of the leaves in the evening when thrips are more active. Repeat at five-day intervals for at least three applications. Blue sticky traps placed among the daylilies help monitor population levels and trap adults. Keep surrounding areas weeded, as thrips overwinter in plant debris and move into the border in spring. Predatory mites (Amblyseius cucumeris) released in early summer provide biological control in smaller gardens.

Aphids

Aphids colonise hemerocallis primarily at the crown and on the emerging new foliage in spring. The insects are often pale green or yellowish and cluster between the tightly packed leaf bases where they are sheltered from predators and weather. Affected emerging leaves curl and may fail to unfurl properly. Established leaves above the crown show honeydew deposits and may develop sooty mould. On healthy, well-grown daylilies, aphid pressure is usually manageable, but young plants or those already stressed by drought or disease can be significantly set back by a heavy infestation before summer flowering begins.

Direct a strong jet of water into the crown of the plant to dislodge aphid colonies from the leaf bases. This is most effective in spring when colonies are just establishing. Follow up with an insecticidal soap spray applied to the crown and the base of the emerging foliage. Repeat after seven days. Hoverflies and ladybirds are effective natural predators on hemerocallis and will reduce populations through the season if broad-spectrum insecticides are not used. Dividing overcrowded daylily clumps every three to four years, which is good practice anyway, also disrupts aphid colonies established in the dense crown of a mature clump.

Drought

Hemerocallis is more drought-tolerant than many herbaceous perennials, but prolonged dry periods in summer cause the long, strap-like leaves to curl inward and tips to brown. Drought stress on daylilies typically shows first as yellowing from the leaf tips downward, accompanied by the characteristic rolling. The rolling reduces the leaf's exposed surface area to slow transpiration. Plants in free-draining soils or those grown in full sun with high wind exposure are most vulnerable. Drought stress reduces the number of flower buds set and may cause early bud drop on plants that are building toward their summer peak.

Water daylilies deeply during dry spells, particularly during bud formation and flowering in early to midsummer. A mulch of bark or garden compost around the clumps retains moisture and also suppresses the weeds that compete for water. Daylilies in heavy soils with good moisture retention are far more drought-resilient than those on light, sandy ground. Once established, most hemerocallis cultivars can survive reasonable drought without permanent damage, but they will produce significantly fewer and smaller flowers in a dry summer. Consistent moisture throughout June and July produces the longest and most prolific display.

Crown rot

Crown rot is a serious disease of hemerocallis caused by soil-borne fungi including Sclerotium rolfsii and Fusarium species. It affects the crown tissue at soil level, where the leaves emerge from the root system. Infected crowns turn soft, brown, or yellow and produce leaves that are stunted, curled, and yellowed from the base upward. The characteristic symptom of Sclerotium crown rot is the presence of small, round, mustard-seed-sized brown structures (sclerotia) at the base of affected stems. In wet weather a white fungal mycelium may also be visible at the crown. Crown rot is most severe in warm, wet conditions and in soils with poor drainage or high organic matter content near the crown.

Act quickly at the first sign of crown rot. Lift the affected plant, remove all soft or discoloured crown tissue with a clean knife, and allow the remaining healthy tissue to air dry for several hours in a shaded position. Dust the cleaned crown with a sulphur fungicide and replant in a fresh position with improved drainage. Do not replant in the same spot where rot occurred without first treating the soil with a fungicide drench. Avoid burying daylily crowns too deeply when planting, as the crown should sit at or just below soil level rather than several centimetres underground. Replant in raised or well-draining ground to reduce the risk of recurrence.

Spider mites

Spider mites attack hemerocallis during hot, dry summers, particularly on plants in full sun with poor air circulation. The mites colonise the undersides of leaves, causing a fine bronze stippling of the upper surface as they extract cell contents. As feeding intensifies, affected leaves curl under at the edges and lose their glossy green colour, taking on a dull, dusty appearance. Fine webbing stretched between leaf bases is the most reliable diagnostic sign. Mite damage on daylilies is often mistaken for drought or rust in the early stages, but the absence of rust pustules and the presence of webbing distinguish it clearly.

Mist daylily foliage with water on hot afternoons to raise humidity and slow mite reproduction. Remove the most badly affected leaves and bin them. Apply neem oil or a miticide spray to all leaf surfaces, concentrating on undersides, in the cool of evening. Repeat at seven-day intervals for three applications. Predatory mites (Phytoseiulus persimilis) provide effective biological control in warmer months and can be introduced when spider mite populations first appear. Keeping the soil consistently moist through summer reduces the dry, stressed conditions that make daylilies most attractive to spider mites.

Frequently asked questions

Why are my daylily leaves curling?

The most common reasons daylily leaves curl are daylily rust, thrips, and aphids. Rust appears as orange pustules on leaf undersides. Thrips cause silver streaking and twisted, curling leaves. Aphids cluster at the crown and on emerging foliage. Drought can also cause leaf rolling in dry summers.

What does daylily rust look like?

Daylily rust (Phakopsora hemerocallidis) appears as small yellow spots on the upper leaf surface with corresponding orange, powdery pustules on the underside. As the disease spreads, leaves curl, yellow, and die back from the tips. Orange powder rubbing off on your fingers confirms rust.

How do I get rid of thrips on daylilies?

Thrips on daylilies are difficult to control because they feed inside flower buds and at the base of leaves. Remove and bin heavily affected leaves. Apply an insecticide labelled for thrips to the crown and leaf bases in the evening. Repeat at five-day intervals for three to four applications. Blue sticky traps help monitor population levels.

Can daylilies recover from crown rot?

Daylilies can recover from mild crown rot if you act quickly. Lift the plant, trim away all soft or discoloured tissue, allow the crown to air dry, dust with a sulphur fungicide, and replant in well-draining soil in a fresh position. Severely affected plants are often best discarded to prevent spread to healthy clumps nearby.