Lavatera Leaves Curling

Mallow rust

Mallow rust (Puccinia malvacearum) is the most common disease of lavatera in UK gardens and one of the most distinctive fungal diseases in any ornamental planting. The rust causes characteristic orange, yellow-brown, or rust-red pustules to appear on the undersides of the leaves, with corresponding pale yellowish or whitish patches on the upper leaf surface directly above each pustule. The pustules are the spore-producing structures of the fungus and release clouds of orange spores that spread rapidly by wind and rain splash to infect further leaves. As the infection progresses, the affected leaves curl, distort, and drop prematurely, with heavily infected plants losing large portions of their foliage in severe outbreaks by late summer. Mallow rust affects all members of the mallow family (Malvaceae) including Malva, Sidalcea, Alcea (hollyhock), and Malope, and can spread between these plants within the same garden. The disease develops most rapidly in warm, humid conditions with limited air circulation around the plants, and in the crowded cottage-garden borders where lavatera is most commonly grown these conditions often prevail. Lavatera that has been hard-pruned in spring and is producing vigorous, rapidly growing new growth in early summer is particularly susceptible, as the soft, rapidly expanding leaf tissue is easier for the rust spores to penetrate than fully mature, thickened foliage.

Remove and bin all affected leaves as soon as rust pustules are noticed; do not compost infected material as the spores remain viable in compost and return to the garden. Apply a sulphur-based fungicide or a copper oxychloride spray at the first signs of infection, and repeat at the interval recommended on the product label. These fungicides are most effective when applied before or in the very early stages of infection; once the pustules are fully developed and spreading, chemical treatment limits but does not eliminate further spread. Improve air circulation around lavatera by spacing plants adequately when planting and by removing surrounding plants that create an overly dense, humid microclimate. Avoid overhead watering, which wets the foliage and provides the moisture film that rust spores require to germinate. At the end of the season, cut lavatera down and remove all fallen leaves from around the plant, as overwintering rust inoculum on the debris is the primary source of the following year's infection. Annual hard pruning in spring removes the stems on which rust spores have overwintered and gives the new growth a clean start.

Powdery mildew

Powdery mildew affects lavatera in late summer, producing a white or grey floury coating on the upper surfaces of the large, lobed leaves and causing the margins to curl upward. The disease is most common in crowded plantings where air circulation is poor or in plants under drought stress at the roots. The large, soft, hairy leaves of lavatera provide a surface that powdery mildew can colonise readily once the microclimate around the leaves is sufficiently warm and humid, and in a mixed border where the plants touch and air cannot move freely through the canopy, mildew can spread rapidly through the plant's foliage. Powdery mildew and rust can appear on the same plant simultaneously in the later part of the growing season, compounding the leaf damage and early senescence of the foliage.

Improve air circulation around lavatera by ensuring adequate spacing between plants. Water at the base of the plant consistently during dry periods, as drought stress increases mildew susceptibility. Remove affected leaves promptly and apply a potassium bicarbonate spray at the first signs of white coating. The annual hard pruning of lavatera in spring, which removes the previous year's growth and resets the plant from a compact crown, opens up the plant structure and reduces mildew pressure in the following season by starting each year with an open canopy that allows good air movement.

Froghoppers

Froghoppers (Philaenus spumarius), the insects responsible for the familiar white froth known as cuckoo spit, occasionally affect lavatera in early summer. The froghopper nymph conceals itself within the white frothy mass and feeds by piercing the stem tissue to extract plant sap, causing wilting and distortion of the shoot tip above the feeding point. On lavatera, which produces soft, rapidly extending new growth in early summer, froghopper damage can cause the affected shoot tips to wilt and curve as the insect drains the sap supply to that part of the stem. The damage is usually limited to individual shoot tips and is not serious enough to affect the overall health or flowering of an established lavatera, but it can cause alarm when first noticed and the cuckoo spit patches on the stems of what should be a vigorous flowering shrub can seem incongruous.

Wipe the froth away with a gloved hand to expose the froghopper nymph and remove it. A jet of water directed at the froth dislodges both the nymph and the protective foam. There is no need for insecticide treatment for froghoppers on lavatera; the damage is minimal and the insects are present for only a few weeks in early summer before completing their lifecycle and flying away as adults. Lavatera is vigorous enough to grow past any froghopper damage within days.

Drought

Drought stress causes lavatera leaves to wilt, lose their normal grey-green tone, and curl inward. Despite lavatera's reputation for a fast-growing, tough, somewhat self-sufficient character in the garden, the large, soft, hairy leaves present a substantial transpiration surface and the plant has a correspondingly significant water demand during the peak of the summer flowering season. Lavatera growing in very free-draining, light soil, in a position where the rain shadow of a wall or fence reduces natural rainfall, or in their first season before their root system is fully established, can show drought stress in hot spells. The pithy, hollow stems of lavatera lose water to the atmosphere more readily than the solid stems of other shrubs of similar size, making water management during establishment important.

Water newly planted lavatera consistently through its first season. Once established, lavatera in average garden soil manages most UK summers without supplementary watering. During prolonged dry spells in the peak of the flowering season, watering at the base of the plant maintains the flower production that is the plant's main ornamental contribution. Mulching at the base retains soil moisture and reduces the extreme soil temperature fluctuations that stress the roots most. Avoid waterlogging, which is more damaging to lavatera than moderate drought.

Root rot

Root rot causes sudden collapse and death in lavatera, often without warning and at any point during the growing season. The pithy, hollow stems of lavatera provide less structural strength against water-pressure-related pathogens than the solid wood of longer-lived shrubs, and root rot from poorly drained soil, crown rots from excessive soil moisture at the stem base, and Phytophthora infections in persistently wet conditions can kill lavatera rapidly. The plant's relatively short natural lifespan, often three to seven years even in good conditions, means that sudden death in an older specimen may simply be the end of its natural life rather than disease, but in younger plants sudden collapse in wet conditions should prompt investigation of the root system. Root rot is distinguished from frost damage, which causes similar sudden collapse, by the season: root rot is most likely to occur in wet conditions at any time of year, while frost damage occurs in winter or spring after cold weather.

Plant lavatera in well-drained soil in full sun. It is native to Mediterranean coastal regions and tolerates poor, dry, sandy soils well, performing better in lean conditions than in rich, moist garden borders where lush, top-heavy growth is more susceptible to root and crown rot. Do not improve the soil excessively before planting lavatera; it thrives in the lean, free-draining conditions that would disappoint most other plants. Keep mulch away from the stem crown to prevent moisture accumulating at the base. If a lavatera dies suddenly in wet conditions, check the root system for rot and improve drainage before replanting; if the plant was several years old, replacing with a new specimen in a slightly different position with better drainage is the most straightforward response.

Frequently asked questions

Why are my lavatera leaves curling?

Mallow rust (Puccinia malvacearum) is the most common disease on lavatera, causing distinctive orange or yellow-brown pustules on the undersides of the leaves with corresponding pale patches on the upper surface and curling of affected leaves. Powdery mildew causes white coating and upward marginal curling in late summer. Froghoppers cause wilting and distortion of individual shoot tips in early summer.

Why does my lavatera have orange spots?

Orange or rust-brown pustules on lavatera leaves are caused by mallow rust (Puccinia malvacearum), a fungal rust disease that affects all members of the mallow family including lavatera, malva, sidalcea, and hollyhock. The pustules appear primarily on the undersides of leaves with pale yellow patches on the upper surface. The affected leaves curl and drop. Remove infected leaves, improve air circulation, and apply a sulphur-based fungicide at the first signs.

Why is my lavatera dying suddenly?

Sudden death of lavatera most often results from root rot caused by waterlogged or poorly drained soil, or from the natural short lifespan of tree mallows in combination with frost damage to the crown in a hard winter. Lavatera is often short-lived even in ideal conditions, typically giving three to seven years of vigorous growth before declining. If a lavatera collapses in wet conditions, root rot is the most likely cause; if it fails to emerge from the base in spring after a cold winter, frost damage to the crown is probable.

Does lavatera need hard pruning?

Yes, lavatera benefits from annual hard pruning in early to mid-spring, cutting all the previous year's stems back to within 20 to 30 centimetres of the main framework or ground level. This removes the frost-damaged, hollow, pithy stems that lavatera produces and stimulates vigorous new growth from the crown. Do not prune in autumn, as this leaves the crown exposed to frost damage over winter; prune in spring when new growth is just beginning to emerge. Hard annual pruning significantly extends the useful life of tree mallow.