Why Are My Jerusalem Artichoke Leaves Curling?

Aphids

Aphids are the most common cause of leaf curling on Jerusalem artichoke in UK gardens. Sunflower aphid and peach-potato aphid colonise the growing tips and undersides of the leaves from May to August, causing dense colonies on the soft young growth. The leaves at the shoot tips curl and pucker tightly around the aphid colonies; the plant produces honeydew which drips onto lower leaves and attracts ants and sooty mould. Large, established plants tolerate moderate aphid pressure without significant loss, but heavy infestations slow the development of new growth at the tops of the tall stems.

What to do

• Natural predators (ladybirds, hoverfly larvae, parasitoid wasps) usually manage aphid populations on outdoor Jerusalem artichokes without intervention. For severe infestations on the growing tips, apply insecticidal soap directly to the colonies. Avoid nitrogen-heavy feeding, which produces soft, aphid-attractive growth.

Powdery mildew

Powdery mildew (Golovinomyces cichoracearum) is almost universal on Jerusalem artichokes in the UK from midsummer. It produces a white, powdery coating on the upper surfaces of the leaves, followed by yellowing and browning of the leaf and curling as the tissue dies. The mildew appears first on the lower, older leaves and progresses upward. Late-season mildew (appearing in September or October) has little impact on tuber yield; mildew appearing in July or August is more damaging and can reduce the harvest.

What to do

• Grow in an open, well-ventilated position to reduce mildew pressure. Avoid heavy nitrogen feeding. Remove badly affected lower leaves. There is no reliably effective fungicide for powdery mildew on Jerusalem artichokes in UK home gardens. Accept late-season mildew as normal and focus on harvesting the tubers, which are unaffected by the foliage disease.

Sclerotinia

Sclerotinia (Sclerotinia sclerotiorum) causes a wet crown rot at the base of Jerusalem artichoke stems in cool, wet conditions. Affected stems collapse and the surrounding leaves yellow, wilt, and curl outward as the crown is destroyed. White fluffy mould and hard, irregular black sclerotia (the resting structures of the fungus) appear at the base of the rotted stem.

What to do

• Remove and destroy affected plants and surrounding soil. Avoid replanting Jerusalem artichokes or other susceptible crops (lettuce, celery, beans, sunflowers) in the same spot for 3 to 4 years. Improve drainage in heavy soils. The tubers of affected plants are usually still edible if harvested promptly before the rot spreads to them.

Drought and wind

Jerusalem artichoke stems grow rapidly to 2 to 3 metres and are susceptible to wind rock and drought stress in exposed positions. In a dry spell the leaves wilt and curl in the afternoon, recovering overnight; in a very dry summer this can be persistent. Wind damage at the tops of the stems causes the growing tips to curl and brown. Staking the stems in exposed positions reduces wind rock stress.

What to do

• Water during prolonged dry spells, particularly in July and August when tubers are developing. Apply a mulch around the base of the stems. In exposed positions, stake or earth up the stems, or grow a shorter-stemmed variety such as 'Dwarf Sunray' that is less prone to wind damage.

Frequently asked questions

Why are my Jerusalem artichoke leaves curling?

Jerusalem artichoke (Helianthus tuberosus) leaves curl most commonly because of aphid infestation, powdery mildew, or sclerotinia. Jerusalem artichokes are related to sunflowers and are susceptible to many of the same pests. Sunflower aphid (Aphis helianthicola) and peach-potato aphid colonise the growing tips and undersides of the leaves in summer, causing the younger leaves at the shoot tips to curl and pucker around dense feeding colonies. Powdery mildew (Golovinomyces cichoracearum) is extremely common on Jerusalem artichokes in the UK from midsummer onwards, producing a white powdery coating on the upper leaf surface; as the infection advances, the leaves curl, yellow, and die. Sclerotinia (Sclerotinia sclerotiorum) causes a wet crown rot in wet seasons, with white fluffy mould and black sclerotia at the base of the stems: affected leaves yellow, wilt, and curl as the crown rots.

How do I grow Jerusalem artichokes in the UK?

Jerusalem artichokes (Helianthus tuberosus) are one of the easiest and most productive crops for UK gardens. Plant tubers 10 to 15 centimetres deep and 30 centimetres apart in a sunny or partially shaded position in any reasonable soil from February to April. The plants grow vigorously to 2 to 3 metres tall and provide a windbreak once established. Water in dry spells; the tall stems may need staking in exposed positions to prevent wind damage. Harvest the tubers from October onwards after the aerial stems have died back, digging as required throughout autumn and winter. The tubers are very hardy in the ground and can be left in the soil until needed. Jerusalem artichokes spread vigorously: any tuber fragment left in the soil regrows the following year, so choose a dedicated spot or be prepared for persistence. Grow a named variety ('Fuseau' is smooth-skinned and easier to peel; 'Dwarf Sunray' is shorter-stemmed and less liable to wind rock) for better culinary quality than the typical knobbly unnamed types.

Why is my Jerusalem artichoke getting powdery mildew?

Powdery mildew on Jerusalem artichokes is almost universal in UK gardens by late summer and early autumn; the plants are highly susceptible and the UK's warm days and cool nights in August and September create ideal conditions for mildew development. The white powdery coating on the leaves (a mass of fungal spores) is not seriously damaging if it appears late in the season when the tubers have already bulked up, but early onset in July or August can reduce tuber yield significantly. Powdery mildew on Jerusalem artichokes cannot be prevented reliably in UK conditions. Planting in a more open position with good air movement, avoiding excessive nitrogen feeding (which produces soft, mildew-prone growth), and removing and composting the worst-affected leaves slows the progression but does not eliminate it. No fungicide is reliably effective on Jerusalem artichoke powdery mildew in UK home garden conditions.

Are Jerusalem artichokes related to artichokes?

No, Jerusalem artichoke (Helianthus tuberosus) is not related to the globe artichoke (Cynara cardunculus var. scolymus) despite sharing part of its common name. Jerusalem artichoke is a species of sunflower, native to North America, grown for its knobbly edible tubers which resemble ginger root or new potatoes. Globe artichoke is a thistle from the Mediterranean. The name 'Jerusalem' is thought to be a corruption of the Italian 'girasole' (meaning sunflower), not a reference to the city; the 'artichoke' part was added because the flavour of the tubers was thought to resemble the heart of a globe artichoke. Jerusalem artichoke is also sometimes called sunchoke, particularly in North America, to avoid confusion with globe artichoke.