Why Are My Eremurus Leaves Curling?

Waterlogging

Waterlogging is the most serious threat to eremurus in UK gardens. The fleshy, starfish-shaped root crown is adapted to the cold, dry winters of Central Asia and deteriorates rapidly in persistently wet, anaerobic UK clay. When the crown rots over winter, the leaves emerge stunted, curl, and collapse in spring before the plant can produce its flower spike. This is by far the most common cause of eremurus failure in the UK, and the primary reason why sharp drainage is the non-negotiable prerequisite for growing eremurus successfully.

What to do

• Plant eremurus in the most sharply drained position available in the garden. A raised bed, south-facing slope, or gravel garden provides ideal drainage. In standard borders in clay-heavy UK gardens, incorporate very generous quantities of coarse grit (at least half the volume of the planting area) before establishing eremurus.
• In particularly wet gardens or heavy clay without good natural drainage, protect the crown from winter wet by placing a pane of glass or a cloche over the planting from autumn until spring, allowing the soil to remain dry while the crown is dormant.
• Mulch the planting area with coarse grit rather than organic mulch, to keep the crown area dry and free-draining through winter.

Late frost damage

Eremurus leaves emerge in early spring and grow rapidly, making them vulnerable to the late frosts that are common in the UK in April and May. Frost-damaged leaves develop brown, papery tips and margins that curl inward as the frozen tissue collapses. In severe late frost, the entire leaf rosette may be killed back to the crown. The plant typically regenerates new growth after mild frost damage, but severe or repeated frost damage weakens the plant and may prevent flowering in that season.

What to do

• Cover emerging eremurus growth with a double layer of horticultural fleece whenever frost is forecast in spring. The leaves emerge earlier than many other border plants and remain vulnerable well into May.
• A wigwam of bamboo canes with fleece draped over the top provides effective frost protection while allowing air circulation. Remove during the day when frost is not forecast.
• In frost-pocket positions, plant eremurus against a south or west-facing wall where the stored heat moderates overnight temperatures.

Crown rot

Crown rot, caused by fungal pathogens, is closely related to waterlogging but can also occur in conditions that are not strictly waterlogged if the crown was damaged during planting. The brittle root arms of the eremurus crown snap very easily, and mechanical damage during planting creates entry points for fungal pathogens. Crown rot causes the strap-like leaves to curl and yellow as the central crown deteriorates and cannot support normal growth. Rotten crowns typically show dark brown, soft tissue when dug up and examined.

What to do

• Handle eremurus crowns with exceptional care during planting, keeping the brittle root arms intact. Do not bend or break the arms when positioning the crown in the planting hole.
• Spread the root arms gently and horizontally in a shallow, wide planting hole so that each arm rests naturally without being bent upward at its tip.
• Dust the crown and root arms with sulphur powder before planting to reduce fungal rot risk. This is particularly worthwhile in any soil that is not completely free-draining.

Aphids

Aphid colonies form on eremurus leaves and flower stems, causing the strap-like leaves to curl as sap is extracted. Heavy infestations on the emerging flower spike can distort the stem and reduce flowering quality. Aphids are most likely during warm, dry spring weather and are a particular problem in sheltered positions against walls where beneficial insects are less prevalent.

What to do

• Check eremurus leaves and emerging flower stems regularly in spring for aphid colonies, particularly on the undersides of the strap-like leaves.
• Knock aphids off with a strong jet of water, directing the spray at the undersides of the leaves. This is effective and causes no damage to the plant.
• Apply insecticidal soap spray to heavy infestations, repeating every three to four days until the population is controlled.

Drought

Although eremurus requires sharp drainage and is adapted to dry summer conditions, drought stress during the spring growing and flowering period causes the strap-like leaves to curl inward to reduce water loss. Eremurus is in active growth from early spring through to June and needs sufficient soil moisture during this period to support the rapid development of its tall flower spike. After flowering and leaf die-back, a dry summer dormant period is actually beneficial.

What to do

• Water eremurus during dry periods in spring and early summer, particularly during flower spike development. The plant's spectacular height and the rapid development of its spike require significant moisture resources during this period.
• Apply a generous mulch of organic matter (but not over the crown itself) in late winter or early spring to help retain soil moisture through the growing season.
• After the leaves have died back in midsummer, allow the soil around eremurus to dry: the summer dormant period is when waterlogging risk is lowest and a dry rest is beneficial.

Frequently asked questions

Why are my eremurus leaves curling?

Eremurus leaves curl most often from late spring frost damage or waterlogging. The strap-like leaves emerge early in spring and are vulnerable to late frosts, which cause the tips and margins to curl and brown. Waterlogging in heavy clay during winter or early spring causes the fleshy, starfish-shaped root crowns to rot, and the leaves curl and collapse as the damaged crown fails to support normal growth.

Why is my eremurus not flowering?

Eremurus fails to flower most often because the root crown was damaged by waterlogging over winter, because the plant is not yet mature enough (newly planted crowns often take two or three years to produce their first full flower spike), because the leaves were damaged by late frost and the plant lacks energy reserves, or because the plant is overcrowded and individual crowns are competing for resources. Ensuring excellent drainage is the single most important factor for reliable eremurus flowering in UK gardens.

When should I plant eremurus?

Plant eremurus crowns in autumn from September to November, with the brittle, octopus-like root arms spread horizontally in a shallow planting hole, so the central crown is just below the soil surface (2 to 3 cm depth). The root arms must not be broken during planting as they are the primary energy storage tissue. Handle the crowns very carefully. Plant in the sunniest, most sharply drained position available in the garden.

How do I protect eremurus from frost?

Protect the emerging eremurus growth from late spring frosts by covering with horticultural fleece when frost is forecast in April and May. The leaves emerge early and extend rapidly, making them vulnerable to the sharp frosts that occur in the UK even in mid-spring. A few nights of severe late frost can damage the emerging foliage significantly and set back the plant for the season. Horticultural fleece provides adequate protection for the temperatures typically encountered in UK late spring frosts.