Why Are My Camassia Leaves Curling?

Waterlogging

Camassia is uniquely adapted to moist, even seasonally wet conditions, but there is still a critical distinction between consistently moist soil (which it loves) and permanently stagnant, anaerobic waterlogging (which damages it). In completely airless, waterlogged soil where water sits without draining for months at a time, camassia bulbs will eventually deteriorate. The broad leaves curl, yellow, and the plant collapses. This is most likely in compacted, impermeable clay in very low-lying positions where water never drains at all, or in containers without drainage holes.

What to do

• Camassia is an excellent choice for heavy, moisture-retentive clay border soil where many other bulbs fail. It does not require improved drainage in the way that most bulbs do.
• The distinction to avoid is truly stagnant, non-draining waterlogging. If water sits visibly on the surface for weeks after rain, or the soil smells anaerobic, even camassia will struggle.
• In genuinely waterlogged positions, incorporate organic matter to improve soil structure and create some pore space, even if overall moisture retention remains high.
• In containers, use a moisture-retentive compost with some drainage capacity and ensure drainage holes are present.

Aphids

Aphid colonies form on camassia leaves and flower stems in spring, causing the broad, strap-like leaves to curl inward as sap is extracted and cell growth becomes uneven. Infested leaves lose their normal upright posture and curl inward along their length. Large aphid populations also excrete honeydew, promoting sooty mould growth on the leaf surface that further weakens the plant by reducing photosynthesis. The distinctive blue-green colour of many camassia species can mask early aphid infestations, so check undersides of leaves regularly in spring.

What to do

• Check camassia regularly in spring for aphid colonies, particularly on the undersides of leaves and at the base of emerging flower stems where infestations typically begin.
• Knock aphids off with a strong jet of water from a hose, directing the stream at the undersides of leaves. This is effective against moderate infestations without chemical intervention.
• Apply an insecticidal soap spray to heavily infested plants, targeting the undersides of leaves. Repeat every three to five days until the population is controlled.
• Encourage natural predators: ladybirds, lacewings, and ground beetles consume aphids rapidly once they establish in the garden.

Bulb rot

Bulb rot caused by Fusarium and other fungal pathogens can affect camassia, particularly in conditions of compacted, airless soil or where bulbs have been stored incorrectly before planting. The large camassia bulbs deteriorate from the base plate upward, producing curling, yellowing leaves in spring as the rotting bulb cannot support normal growth. This is most common in bulbs that were purchased in poor condition or stored damp for extended periods.

What to do

• Purchase firm, plump camassia bulbs from a reputable supplier and plant promptly in autumn. Inspect before planting and discard any that are soft, smell of rot, or show significant brown discolouration.
• Plant camassia at 10 to 15 cm depth: the relatively deep planting provides some protection against surface fungal pathogens.
• Improve soil structure in compacted positions by incorporating organic matter. Even a moisture-retentive soil should have good structure to allow oxygen exchange.

Drought at flowering time

Camassia is naturally adapted to moist spring conditions and although it tolerates summer drought in dormancy, drought stress during the spring growing and flowering period causes the broad leaves to curl inward to reduce water loss. This is relatively unusual in UK springs but can occur during warm, dry spells in late April and May just as camassia is approaching its peak flowering. The leaves lose their upright posture and curl along their length as the plant conserves water.

What to do

• Camassia planted in moisture-retentive clay or humus-rich soil rarely needs supplementary watering in UK springs. The natural soil moisture of suitable positions is usually sufficient.
• In lighter, sandy, or well-drained soils, water camassia during dry periods in spring to maintain the moist conditions it prefers. A thorough soaking once or twice a week is more effective than frequent shallow watering.
• Applying a generous mulch of garden compost around camassia in early spring helps retain soil moisture through the growing and flowering season.

Overcrowding

Camassia increases over time by producing offset bulbs, and established colonies become congested after several years. Overcrowded camassia plants produce progressively smaller, weaker, more curling leaves as individual bulbs compete for resources. Flower spike height and quality decline in very congested clumps. Division restores vigour and is also an opportunity to spread the planting across a wider area.

What to do

• Divide camassia clumps every four to five years, in late summer or early autumn when the bulbs are dormant after the leaves have died back completely. Lift the clump, separate individual bulbs, and replant at 10 to 15 cm apart.
• Enrich the replanting area with garden compost or leafmould to restore soil organic matter.
• Offset bulbs can be planted in new positions to extend the naturalistic drift across the border or meadow area.

Frequently asked questions

Why are my camassia leaves curling?

Camassia leaves curl most often from waterlogging or aphid infestation. Although camassia naturally grows in damp meadows in North America and tolerates moist conditions well, persistently waterlogged, anaerobic soil causes the bulbs to deteriorate and the broad, strap-like leaves to curl and yellow. Aphid colonies on the leaves and flower stems cause the foliage to curl inward as sap is extracted, and the leaf tissue loses its normal turgidity.

What conditions does camassia need?

Camassia thrives in moist, humus-rich soil in full sun or light partial shade. It naturally grows in seasonally wet North American prairies and meadows, so it is an excellent choice for damp borders, pond margins, and moisture-retentive clay soil in UK gardens where many other bulbs struggle. Camassia is one of the few large-flowered bulbs that actively performs well in wet clay. Plant in autumn and divide every few years to maintain vigour.

When should I plant camassia bulbs?

Plant camassia bulbs in autumn from September to November at a depth of 10 to 15 cm. The large bulbs need to be planted relatively deep to anchor themselves and to allow the tall flowering stems to remain stable. Space bulbs at 10 to 15 cm apart in bold drifts for the best effect. Camassia performs especially well in heavy, moisture-retentive clay soil that suits its native prairie habitat, and naturalises readily to form impressive colonies.

Can camassia grow in wet soil?

Yes, camassia is one of the best large-flowered bulbs for consistently moist to wet soil. Unlike most spring bulbs, which require free-draining conditions, camassia tolerates and even prefers reliably moist soil that remains damp through spring. It performs well at pond margins, in bog garden borders, in damp meadow areas, and in heavy clay soil. However, it still requires some oxygen exchange and will not thrive in permanently stagnant, completely anaerobic waterlogging.