Why Are My Guava Leaves Curling?

Red spider mite

Red spider mite (Tetranychus urticae) is the most common pest of greenhouse-grown guava in the UK. It produces pale, grey-bronze stippling on the upper leaf surface, with fine webbing on the undersides; affected leaves curl downward, yellow, and eventually drop. The undersides of guava leaves have a dense network of veins that provides shelter for mite colonies. In warm, dry greenhouse conditions, spider mite populations can build rapidly and defoliate a guava plant within a few weeks.

What to do

• Introduce Phytoseiulus persimilis predatory mites at the first sign of infestation. Increase humidity by misting the foliage, particularly the undersides of leaves, and standing the pot on a gravel tray with water. Remove heavily webbed leaves. Treat with a plant-safe miticide spray if necessary before releasing biological controls; wait 48 hours before introducing predators.

Guava wilt

Guava wilt (Fusarium oxysporum f. sp. psidii) is a soil-borne disease that enters through the roots and blocks the vascular system of the tree. The first sign is typically yellowing and wilting of leaves on one branch or one side of the plant, which spreads rapidly; the leaves curl as they lose water, then drop. Cutting a wilting stem reveals brown or orange-brown discolouration of the wood beneath the bark. Plants can decline from apparently healthy to severely wilted in a matter of days in warm conditions.

What to do

• Remove and destroy infected plants promptly. Replace the growing medium entirely before replanting. Ensure excellent drainage; the disease thrives in waterlogged conditions. There is no effective fungicide treatment once wilt is established. New plants should be grown in clean, fresh compost and the containers should be sterilised before reuse.

Cold and draught

Guava is sensitive to cold; temperatures below 10°C cause the leaves to yellow and curl at the margins, and temperatures below 5°C cause lasting damage. Cold draughts in conservatories or unheated greenhouses in autumn and winter are a common cause of leaf drop and curl on guava. In winter, reduce watering and keep the plant on the dry side; the main risk from winter is a combination of cold, wet compost and chilly air, which mimics the conditions in which Fusarium thrives.

What to do

• Move guava to the warmest available position in autumn. Maintain temperatures above 10°C through winter and above 18°C for active growth. Reduce watering in winter. Protect from draughts from doors and vents.

Nutrient deficiency

Iron and magnesium deficiency are both common in guava grown in alkaline or heavily limed compost, or watered with hard tap water. Iron deficiency causes interveinal chlorosis of the youngest leaves (the leaves turn yellow between the dark green veins); magnesium deficiency causes the same pattern on older leaves. Both deficiencies can cause the leaves to become brittle and curl as the affected tissue deteriorates.

What to do

• Use rainwater or filtered water for guava wherever possible. Use an ericaceous (acid) compost, which maintains the slightly acidic pH (5 to 6.5) guava prefers. Apply a chelated trace element foliar feed to correct iron deficiency; apply a magnesium sulphate (Epsom salts) foliar spray at 20g per litre fortnightly to correct magnesium deficiency.

Frequently asked questions

Why are my guava leaves curling?

Guava (Psidium guajava) leaves curl most commonly because of red spider mite, guava wilt (Fusarium oxysporum), or cold and low humidity in UK indoor conditions. Red spider mite (Tetranychus urticae) is the most common pest of guava grown under glass in the UK; the mites colonise the undersides of the leathery, strongly-veined guava leaves and produce pale stippling, bronze discolouration, and fine webbing; affected leaves curl downward and drop. Guava wilt (caused by Fusarium oxysporum f. sp. psidii) is a soil-borne fungal disease that attacks the root system and vascular tissue, causing rapid yellowing and wilting of the leaves (which curl as they lose turgidity) from one side of the plant initially, spreading to the whole tree; infected plants decline quickly and may die within weeks. Cold temperatures below 10°C cause guava leaves to yellow, curl, and drop as the tropical plant is stressed; temperatures below 5°C cause lasting damage.

Can I grow guava in the UK?

Guava (Psidium guajava) can be grown in the UK in a heated greenhouse, large conservatory, or on a very warm, south-facing sheltered wall in the mildest coastal locations. It is not frost-hardy (damaged below 5°C) but tolerates brief temperature dips to 10°C without lasting harm. Guava grows vigorously and can become a large shrub or small tree if not pruned; in a UK heated greenhouse it can be kept to container size with regular pruning after fruiting. Grow in a large pot of well-drained, slightly acidic compost in a very bright position. Guava flowers on new growth and will fruit in a UK greenhouse with hand-pollination; the fruit takes 3 to 4 months to ripen. Water generously in summer and reduce in winter; feed with a balanced fertiliser in spring and summer. Strawberry guava (Psidium cattleianum) is a compact, more cold-tolerant species (to about 0°C) that performs better than common guava in UK conditions.

What does guava wilt look like?

Guava wilt (Fusarium oxysporum f. sp. psidii) typically begins with yellowing and wilting of leaves on one branch or one side of the plant, which then spreads to the rest of the tree over days to weeks. The affected leaves curl and drop; the bark may crack and the wood beneath shows a brown-orange discolouration of the vascular tissue when cut. Infected trees may produce a gummy exudate on the stem surface. The whole plant wilts and dies rapidly in warm, humid conditions; the disease progresses more slowly in cooler UK conditions but is ultimately fatal to infected plants. There is no effective fungicide treatment; infected plants should be removed and the growing medium replaced before replanting.

Why are my guava leaves turning yellow?

Yellowing guava leaves in the UK are most commonly caused by iron or magnesium deficiency, overwatering, or cold stress. Iron deficiency (interveinal chlorosis) causes the younger leaves at the growing tips to turn yellow between the veins while the veins themselves remain green; it is common in guava grown in alkaline compost or watered with hard tap water, which locks up iron. Magnesium deficiency causes older leaves to yellow between the veins, with the veins remaining green. Overwatering causes general yellowing and dropping of both young and old leaves as the root system becomes anaerobic and begins to rot. Cold stress (below 10°C) causes yellowing and leaf drop, particularly of older leaves. Check the compost pH (guava prefers pH 5 to 6.5) and drainage, use rainwater if possible, and feed with a chelated trace element fertiliser if mineral deficiency is suspected.