Why Are My Maianthemum Leaves Curling?

Drought stress

Drought is a very common cause of maianthemum leaf curl. The large, broadly lance-shaped leaves have a significant surface area and transpire freely, and the plant requires consistently moist, humus-rich, cool soil to maintain healthy growth. In dry conditions, the leaves curl inward along their length, the normally rich green colour fades to a paler, duller tone, and the tips of the leaves may develop brown, papery patches. Drought stress is most likely in full sun or partial shade with afternoon exposure, in shallow soil, or during dry UK summers. Even in generally shaded positions, maianthemum can suffer from localised drought under dense, rain-shadow-creating trees.

What to do

• Water maianthemum during dry periods through spring and early summer, when the plant is in active growth and most sensitive to moisture stress.
• Apply a generous mulch of leafmould or well-rotted garden compost, at least 8 cm deep, around the plants each spring. This is the single most effective thing you can do to prevent drought stress in an established planting.
• Ensure the position provides adequate shade: the canopy of deciduous trees significantly reduces soil evaporation and creates the cool, moist microclimate that maianthemum requires.
• In positions where summer drought is a recurring issue, consider repositioning maianthemum to a spot where the soil remains moist more reliably through the season.

Vine weevil

Vine weevil larvae are a significant underground pest of maianthemum. The white, C-shaped larvae hatch from eggs laid in the soil in summer and feed on the rhizomes through autumn and winter, causing the root system to deteriorate. In spring, affected plants produce weak, curling, yellowish stems that fail to reach their full height, or fail to emerge at all if the rhizomes are severely damaged. The characteristic signs of adult vine weevil are also visible on the foliage: distinctive notched scalloping on the leaf margins from adult weevil feeding in summer evenings.

What to do

• Apply biological nematode control (Steinernema kraussei) to the soil around maianthemum in early autumn, when soil temperatures are between 5 and 12 degrees Celsius. This is the timing when newly hatched vine weevil larvae are smallest and most susceptible to nematode infection.
• Apply a second nematode treatment in spring if the autumn treatment was not applied or if damage is severe, to control any larvae that survived winter.
• When lifting and dividing maianthemum, inspect the soil for the characteristic white, C-shaped larvae with an orange-brown head capsule, and destroy any found. Each larva you remove prevents future generations.
• Avoid growing maianthemum in pots, as vine weevil populations build up rapidly in container compost. If growing in containers, use a vine-weevil-resistant compost and apply nematodes regularly.

Slug damage

Slugs attack maianthemum both on the emerging shoots in spring and on the large, soft leaves through summer. The broad leaves are particularly attractive to slugs and provide a significant food source. Slug feeding causes holes in the leaf blade and the affected areas to curl as the damaged tissue collapses. In severe cases the entire leaf surface can be reduced to a skeleton of veins. The shaded, moist, humus-rich conditions that maianthemum prefers are exactly the conditions where slugs thrive in abundance.

What to do

• Apply biological nematode slug control (Phasmarhabditis hermaphrodita) in spring and again in early autumn to target the soil-dwelling slug population around maianthemum plantings.
• Hand-collect slugs in the evening with a torch, particularly in wet spring weather. Regular evening checks during the peak damage period of April to June are the most effective manual control.
• Iron-phosphate slug pellets are safe to use around maianthemum and within the wider garden ecosystem.

Late frost damage

Maianthemum is a very hardy plant but the emerging shoots in spring are frost-sensitive. A late frost in April or May can cause the new growth to curl, blacken, and collapse. Established plants with healthy rhizomes typically regenerate new growth after mild frost damage, but a severe late frost that kills the emerging stem can cost the plant a full season's growth and significantly reduce flower and berry production. The broad flower plume at the tip of each stem is particularly vulnerable to late frost once expanded.

What to do

• Cover emerging maianthemum growth with horticultural fleece when hard frost is forecast in April and May.
• The overhead canopy of deciduous trees provides excellent natural frost protection from radiation frost, which is why maianthemum naturalises so successfully in woodland gardens.
• Maintain a deep mulch over the planting area through winter to delay emergence slightly, reducing the window of vulnerability to late frosts.

Too much sun

Maianthemum is a shade-demanding plant and performs poorly in full sun or exposed south-facing positions. In too much sun, the large leaves curl inward, develop scorched pale patches on the upper surface, and the plant produces notably smaller, weaker stems than healthy specimens in appropriate shade. The foliage takes on a yellowish or bleached appearance instead of its characteristic rich, deep green. The broad leaf area that makes maianthemum so impressive in shade makes it particularly vulnerable to sun scorch.

What to do

• Relocate maianthemum to a position under deciduous trees, or on the north or east-facing side of structures where it receives shade from midday onwards.
• East-facing positions that receive morning sun but afternoon shade are generally acceptable, particularly in moisture-retentive soil.
• If the position cannot be changed, provide temporary shade using shade cloth through the hottest summer months while maintaining generous watering.

Frequently asked questions

Why are my maianthemum leaves curling?

Maianthemum leaves curl most often from drought stress or vine weevil larva damage to the rhizomes. Drought causes the lance-shaped leaves to curl inward to reduce moisture loss, as maianthemum naturally grows in cool, moist, humus-rich woodland conditions. Vine weevil larvae damage the rhizomes in autumn and winter, causing the plant to emerge weakly in spring with curling, yellowing leaves as the root system is insufficient to support normal growth.

What is maianthemum (false Solomon's seal)?

Maianthemum racemosum, false Solomon's seal, is a woodland perennial with arching stems, broad lance-shaped leaves, and plumes of small, creamy-white, fragrant flowers in May and June. It was formerly classified as Smilacina racemosa. The flowers are followed by clusters of attractive, initially green, then red-speckled and finally deep red berries in late summer. It naturalises well under deciduous trees to form impressive colonies, and is one of the most beautiful of all woodland-floor perennials for UK shade gardens.

What conditions does maianthemum need?

Maianthemum thrives in cool, moist, humus-rich, well-drained soil in dappled shade or deep shade. It performs best in soil enriched with generous quantities of leafmould or well-rotted garden compost, and requires consistent moisture through the spring and early summer growing period. It is very hardy in UK conditions and will naturalise freely in suitable woodland-garden settings. Avoid planting in full sun or dry, exposed positions where the large leaf area leads to rapid moisture loss.

How do I treat vine weevil in maianthemum?

Treat vine weevil in maianthemum by applying biological nematode control (Steinernema kraussei) to the soil around the plants in early autumn and again in spring, when soil temperatures are between 5 and 20 degrees Celsius. This is the most effective and garden-safe control method for vine weevil larvae in outdoor plantings. Dig around affected plants to look for the characteristic white, C-shaped larvae in the soil around the rhizomes. Discard heavily damaged rhizomes and treat the remaining healthy parts of the colony.