Why Are My Mesembryanthemum Leaves Curling?

Overwatering

Overwatering is the most common cause of mesembryanthemum failure in UK gardens. As a plant from the arid regions of South Africa, Livingstone daisy is highly adapted to dry conditions and the fleshy, slightly succulent leaves store moisture. In persistently wet soil or in containers without adequate drainage, the shallow root system deteriorates very rapidly. The fleshy leaves become soft, turn yellow, and curl. The plant may collapse entirely. Overwatering is most likely during a typical wet UK summer, particularly in heavy clay soil or in containers placed where rain falls directly into them. This is the single most important growing condition to get right with mesembryanthemum.

What to do

• Plant mesembryanthemum only in extremely free-draining soil. Add coarse grit or sharp sand generously to improve drainage in any soil that is not already light and sandy.
• In containers, use a cactus or succulent compost blended with additional perlite and ensure large drainage holes. Raise containers on pot feet to allow drainage.
• In the open ground during a wet summer, do not water at all: rainfall in a normal UK summer is more than sufficient for established mesembryanthemum.
• Avoid covering plants with cloches or polytunnel cover that traps humidity around the fleshy leaves.

Aphid infestation

Aphids are the most common pest on mesembryanthemum. They colonise the shoot tips and the undersides of the fleshy, glistening leaves, causing them to curl and distort. The glistening surface of the leaves (caused by thousands of tiny crystal cells) can make aphid colonies harder to spot until they are already well established. Green aphids and black bean aphid are both found on Livingstone daisy. Heavy infestations can significantly impair flowering and distort the spreading shoot tips.

What to do

• Check the shoot tips and the undersides of the fleshy leaves regularly from early summer, looking carefully against the glistening leaf surface.
• Spray with insecticidal soap every four to five days for two to three weeks, ensuring thorough coverage of the undersides of the fleshy leaves.
• A jet of water dislodges aphids from the smooth, fleshy leaves very effectively as a first response.
• Spray in the evening: mesembryanthemum flowers attract beneficial insects during the day including hoverflies whose larvae consume aphids.

Cold stress

Cold stress is a significant problem for mesembryanthemum. As a half-hardy annual from South Africa, it cannot tolerate frost at any stage and is damaged by consistent nighttime temperatures below 10 degrees Celsius. Cold causes the fleshy leaves to become soft, take on a slightly translucent appearance, and curl. The characteristic glistening surface of the leaves dulls. Plants that have been planted out too early in spring often fail to thrive for several weeks until temperatures rise. Cold, wet conditions together are particularly damaging.

What to do

• Do not plant mesembryanthemum outside until late May or early June when nighttime temperatures are reliably above 10 degrees Celsius and frosts have passed.
• Harden off for at least two weeks before planting out: mesembryanthemum is sensitive to the sudden transition from protected growing conditions.
• If cold nights are forecast after planting, cover with fleece. Remove it during the day to allow full sun exposure.

Drought stress

Although mesembryanthemum is highly drought tolerant, extreme drought in containers with very limited compost volume can still cause the fleshy leaves to become soft and lose their characteristic turgidity. The leaves may curl slightly and the plant's overall vigour and flowering reduces. In the open ground in well-drained soil, mesembryanthemum rarely suffers from drought in UK conditions, but container plants need monitoring during very hot spells.

What to do

• In the open ground, mesembryanthemum rarely needs watering once established. Intervene only during exceptional drought conditions.
• Container plants: water sparingly when the entire compost block has dried. The fleshy leaves indicate mild drought stress before it becomes damaging.
• Never water on a schedule: always check the compost before watering and only water when clearly dry throughout.

Powdery mildew

Powdery mildew occasionally affects mesembryanthemum later in the season, particularly when conditions alternate between dry and humid. The fleshy leaves develop a white powdery coating and curl slightly. It is less common than overwatering problems but can occur on crowded plants or in sheltered positions with poor air circulation in late summer.

What to do

• Space plants at 25 to 30 cm to ensure adequate air flow between the spreading mats of foliage.
• Remove badly affected shoots and spray healthy growth with a sulphur-based fungicide.
• Ensure drainage is excellent: plants stressed by poor drainage are more susceptible to secondary fungal problems including powdery mildew.

Frequently asked questions

Why are my mesembryanthemum leaves curling?

Mesembryanthemum leaves curl most often from overwatering or aphid infestation. Overwatering in poorly drained soil causes the succulent-like leaves to become soft, yellow, and curl as the shallow root system deteriorates. Aphids colonise the shoot tips and the undersides of the fleshy leaves, causing curling and distortion. As a South African plant adapted to dry, sunny conditions, mesembryanthemum is far more susceptible to overwatering than drought.

Why won't my Livingstone daisy flowers open?

Mesembryanthemum flowers open only in full sun and close in shade, dull weather, and at night. This is entirely normal behaviour. If the flowers remain closed during the day, the position receives too much shade or the weather is too cloudy. Livingstone daisy requires direct, bright sunlight to open its flowers. In a cloudy UK summer, even plants in the sunniest positions may have flowers that open only partially.

When should I sow mesembryanthemum?

Sow mesembryanthemum under glass from February to April at 18 to 21 degrees Celsius. Surface sow and do not cover the seed, as it needs light to germinate. Germination is rapid and the seedlings grow quickly. Harden off carefully for two weeks before planting outside in late May or early June after the last frost, in the sunniest, most free-draining position available.

Does mesembryanthemum need deadheading?

Regular deadheading of mesembryanthemum prolongs the flowering season and prevents the plant from running to seed prematurely. Remove spent flower heads once the petals have dropped. However, the sheer number of flowers on a well-grown plant can make thorough deadheading impractical. A light trim of the whole plant with scissors when it starts to look untidy encourages a fresh flush of flowers and new growth.