Osteospermum Leaves Curling

Aphids

Aphids are the most common pest on osteospermum and a frequent cause of curling leaves. Large colonies of pale green or blackish aphids build up rapidly on the soft new shoots and flower stems, particularly in late spring and early summer. The youngest leaves at the growing tips curl inward and downward around the colonies, making the insects difficult to spot without looking closely. A sticky coating of honeydew on the leaves below the colonies is a reliable sign, and sooty mould often follows. Heavy infestations weaken the plant and reduce flower production significantly.

Treat aphids on osteospermum early before colonies become established inside the curled leaves. A strong blast of water from a hose dislodges most insects immediately and is especially effective on plants in containers, where you can tilt the pot to reach all sides. Follow up with an insecticidal soap spray applied thoroughly to all stem tips and the insides of curled foliage. Repeat every five to seven days for three rounds. Encouraging natural predators, particularly hoverflies and ladybirds, by growing nearby umbellifers helps keep populations in check throughout summer.

Whitefly

Whitefly is a persistent and very common pest of osteospermum, particularly on container-grown plants kept on patios or in conservatories. When you brush against an affected plant, a cloud of tiny white-winged flies lifts from the leaf undersides. The immature scale-like nymphs feed on the undersides of leaves, excreting honeydew and causing the leaves to curl downward and yellow. Unlike aphids, which tend to concentrate on new growth, whitefly affects older mid-height leaves more uniformly. Once established, populations can be difficult to eliminate because adults, nymphs, pupae, and eggs are all present simultaneously and at different stages of susceptibility.

Use yellow sticky traps hung among the foliage to monitor and trap adult whitefly. To treat the nymph population on leaf undersides, spray with insecticidal soap or a natural pyrethrin spray, covering undersides thoroughly and repeating every five to seven days. Because whitefly eggs hatch over several weeks, four to six applications are often needed to break the cycle completely. In conservatories, the biological control Encarsia formosa, a parasitic wasp, is highly effective when introduced early in the season before populations peak. Improve ventilation around container plants to make conditions less hospitable.

Spider mites

Spider mites attack osteospermum in hot, dry conditions, especially on plants in sheltered positions with poor air movement. The mites colonise the undersides of leaves and feed by piercing cells, leaving a bronze, stippled discolouration across the upper surface. As feeding intensifies, leaves curl under at the edges and the plant loses its fresh, glossy appearance. Fine webbing linking leaf axils and stems is the definitive diagnostic sign, distinguishing mite damage from drought stress or nutrient deficiency.

Raise humidity by misting the foliage with water in the morning and ensuring the compost or soil does not dry out completely. Remove the most heavily affected leaves and bin them. Apply a neem oil solution or miticide spray to all surfaces, particularly undersides, in the cool of evening to prevent scorch. Repeat at seven-day intervals for three treatments. Moving containers to a slightly more open position with better air movement helps prevent reinfestation, as mites thrive in the still, warm air against a south-facing wall.

Drought

Osteospermum has good drought tolerance once established in the ground, but container-grown plants can dry out very rapidly in warm weather and show stress quickly. When compost dries completely, the leaves curl inward and upward, taking on a dull, grey-green colour rather than their usual bright green. Tips may turn brown and the plant stops producing new buds. The curling is a moisture-conservation response and is most noticeable in the hottest part of the afternoon, with some recovery in the early morning.

Water container osteospermum generously in warm weather, until water runs freely from the drainage holes. In the height of summer, pots may need watering daily. Adding a water-retaining gel to the compost at planting time significantly reduces the frequency needed. In borders, a bark mulch layer around the plants slows evaporation. Osteospermum flowers best when kept consistently moist during bud development, so avoiding cycles of drought and waterlogging produces the longest and most prolific display.

Powdery mildew

Powdery mildew can affect osteospermum in late summer, particularly where plants are crowded together or positioned against a wall where air movement is poor. The disease appears as a white or pale grey floury deposit on the upper leaf surface. Affected leaves curl slightly at the margins and lose their colour. The infection usually starts on the lower and inner leaves where air circulation is weakest and works outward. A mildew outbreak rarely kills osteospermum but reduces the vigour and appearance of the plant during what should be its peak late-summer flowering period.

Deadhead and tidy osteospermum regularly to maintain good air movement through the plant. Space container plants so their foliage does not overlap. At the first sign of mildew, remove affected leaves and spray with a bicarbonate of soda solution (one teaspoon per litre of water with a few drops of dish soap), repeating weekly. Potassium bicarbonate fungicides give more reliable results in persistent cases. Avoiding overhead watering reduces the leaf wetness that encourages spore germination in the first place.

Root rot

Root rot is a significant risk for osteospermum grown in containers with insufficient drainage or left standing in water. The disease sets in when the root zone becomes waterlogged and anaerobic for extended periods. Above ground, the first signs are leaves that curl, wilt, and yellow despite the compost feeling moist. Unlike pest-related curling, root rot affects the whole plant uniformly and the wilting does not recover overnight. The stem base may feel soft and discoloured at soil level in severe cases.

Remove the plant from its pot and examine the root ball. Healthy osteospermum roots are white or cream. Rotted roots are brown or black, slimy, and may smell unpleasant. Trim away all affected roots with clean scissors, allow the cut surfaces to air-dry briefly, and repot in fresh, free-draining compost with extra perlite mixed in. Ensure the new pot has large drainage holes and raise it on pot feet to allow water to flow freely. Water carefully after repotting, letting the top centimetre of compost dry slightly between waterings until the plant shows new growth.

Frequently asked questions

Why are my osteospermum leaves curling?

The most common reasons osteospermum leaves curl are aphids on stem tips and whitefly infestations. Check the undersides of leaves for clusters of insects or a cloud of tiny white flies. Drought and spider mites are also common causes in hot weather.

How do I get rid of whitefly on osteospermum?

Yellow sticky traps catch adult whitefly. For the larvae on leaf undersides, spray with insecticidal soap or a pyrethrin-based spray, covering undersides thoroughly. Repeat every five to seven days for three to four applications as eggs hatch in waves.

Why are my African daisy leaves curling and going yellow?

Curling combined with yellowing on osteospermum usually indicates whitefly, a heavy aphid infestation, or root rot from waterlogged compost. Check for insects first, then inspect the roots if no pests are present.

Can osteospermum get powdery mildew?

Yes, osteospermum can develop powdery mildew in late summer, especially in humid conditions with poor air circulation. Leaves develop a white floury coating and curl at the edges. Improve airflow and spray with a bicarbonate of soda solution weekly.