Why Are My Nectaroscordum Leaves Curling?

Aphids

Aphids are the most common cause of nectaroscordum leaf curl. Dense colonies of aphids, sometimes including the mottled arum aphid (Aulacorthum circumflexum) and other species, form on the undersides of the long, keeled leaves in spring, causing the foliage to curl inward along its length as sap is extracted and cell growth becomes uneven. The flower stems can also be infested, and in heavy infestations the flowering stem may be weakened and fail to achieve its full height. Aphid honeydew promotes sooty mould on the leaf surface. The garlic scent of crushed nectaroscordum foliage deters some pests but does not deter aphids.

What to do

• Check nectaroscordum regularly in spring for aphid colonies on the undersides of the long, keeled leaves and on the emerging flower stems.
• Apply a strong jet of water to knock aphids off, directing the spray at the undersides of the leaves. This is effective and avoids chemical intervention. Repeat every few days until the colony collapses.
• Apply insecticidal soap spray to persistent heavy infestations. Neem oil spray is also effective and has a repellent effect that discourages reinfestation.
• Ladybirds and lacewings consume aphid colonies rapidly: encourage them by providing habitat such as log piles and insect hotels.

Waterlogging

Waterlogging in heavy, poorly drained clay causes nectaroscordum bulbs to deteriorate. The long, keeled leaves curl and yellow as the rotting bulb base fails to support normal growth. Nectaroscordum is native to Mediterranean woodland margins and is adapted to well-drained, humus-rich soil that dries in summer. While it tolerates reasonably moist conditions through its spring growing period, it cannot survive in persistently anaerobic, waterlogged soil. Container plants without drainage are particularly at risk.

What to do

• Plant nectaroscordum in well-drained soil. In heavy clay, incorporate generous quantities of coarse grit and garden compost before planting.
• Nectaroscordum performs very well in lightly shaded woodland-edge conditions with good drainage, which closely mimics its Mediterranean habitat.
• Avoid low-lying, impermeable positions. A position that dries somewhat in summer, when nectaroscordum is dormant, is ideal.

Bulb rot

Fungal bulb rot causes nectaroscordum leaves to curl, yellow, and collapse. The bulbs deteriorate from the base upward in wet conditions, and the characteristic garlic scent becomes noticeably more pungent when a bulb begins to rot as the cell structure breaks down. Bulb rot is most common in bulbs planted in waterlogged soil or in purchased bulbs already in poor condition.

What to do

• Purchase plump, firm nectaroscordum bulbs and plant promptly in autumn. Inspect before planting and discard any that are soft, show brown or discoloured basal plates, or smell of active rot.
• Dust with sulphur powder before planting in any soil that is not completely free-draining.
• Ensure good drainage: this is the most effective preventive measure against nectaroscordum bulb rot.

Leek moth

Leek moth (Acrolepiopsis assectella) occasionally attacks nectaroscordum and other allium relatives. The small, pale caterpillars mine inside the leaves, producing characteristic pale, papery windowed patches and causing the leaf to curl and distort around the damaged area. Leek moth is an increasing problem in southern England following its spread from the Continent, and allium relatives including nectaroscordum are susceptible. The damage is more cosmetic than severe in most cases, but heavy infestations weaken the plant.

What to do

• Cover nectaroscordum with fine insect mesh from late March to prevent the adult moths from laying eggs. The mesh must be fine enough to exclude the small adult moth.
• Remove and destroy any leaves showing the characteristic pale, windowed mining damage to reduce the population before the caterpillars pupate.
• Apply a product containing Bacillus thuringiensis (Bt) biological control to infected foliage as an alternative to chemical control. This is effective against the young caterpillars.

Overcrowding

Nectaroscordum self-seeds prolifically in suitable conditions and can form dense colonies over several years. Overcrowded plants produce progressively weaker, more curling leaves as individual bulbs compete for resources, and the flowering performance of congested plants declines. Self-sown seedlings take three to four years to reach flowering size, and old overcrowded plantings can have a high proportion of non-flowering seedlings contributing to the congestion.

What to do

• Remove excess self-sown seedlings in autumn or early spring before they become established. Nectaroscordum seedlings are small and relatively easy to hoe off when young.
• Deadhead spent flower stems before seeds disperse if the self-seeding is becoming invasive in your garden. The upright seed heads are architecturally attractive so this is a trade-off worth considering.
• Divide congested established clumps every four to five years in late summer when the bulbs are dormant. Lift, separate, and replant at wider spacing.

Frequently asked questions

Why are my nectaroscordum leaves curling?

Nectaroscordum leaves curl most often from aphid infestation or waterlogging. Aphids colonise the leaves in spring, causing the long, narrow, keeled leaves to curl inward as sap is extracted. Waterlogging in heavy clay causes the bulbs to deteriorate and the leaves to curl and yellow. Both problems are common in UK gardens, with aphids being the more frequent cause of leaf distortion on established plants.

What is nectaroscordum?

Nectaroscordum siculum (Sicilian honey garlic) is an allium relative producing tall, elegant stems topped with loose umbels of nodding, bell-shaped flowers in May and June, each flower cream or white with distinctive pink and green markings. The flowers face downward before and after flowering but turn upward as the seed heads develop, creating an attractive architectural effect that persists through summer. Nectaroscordum is increasingly popular in naturalistic and prairie-style planting schemes, where its relaxed habit and long-lasting seed heads add months of interest.

When should I plant nectaroscordum bulbs?

Plant nectaroscordum bulbs in autumn from September to November at a depth of 10 to 15 cm in well-drained soil in full sun or light partial shade. Nectaroscordum is one of the easiest and most reliably naturalising of all ornamental allium relatives in UK gardens. It self-seeds prolifically in suitable conditions and can spread widely, so consider position carefully if a spreading colony is not desired. The seed heads are attractive and can be left in place through summer for structural interest.

Does nectaroscordum smell of garlic?

Yes, nectaroscordum foliage has a characteristic garlic smell when crushed or bruised, as it is closely related to allium. The smell is only released when the leaves are physically damaged, not simply when walking past the plant. The flowers have a more pleasant, faintly sweet scent attractive to pollinators. The garlic scent of the foliage provides some natural protection against deer and rabbits, which typically avoid plants with strong allium-family odours.