Plant problems

Why Are My Aronia Leaves Curling?

Q: Why are my aronia leaves curling?

Aronia (Aronia melanocarpa), also called black chokeberry, leaves curl most commonly in the UK because of aphid infestation, leaf spot, or drought stress. Aronia is one of the hardiest and most disease-resistant fruit shrubs grown in UK gardens, and serious pest or disease problems are relatively rare; however, the rose aphid (Macrosiphum rosae) and other aphid species can colonise the new growth in spring, causing the leaves to curl and distort at the shoot tips. Leaf spot fungi, including Cercospora aronia and Septoria-type fungi, can cause small brown or purple spots on the leaves that spread in wet conditions; affected leaves may yellow and drop prematurely, and when multiple spots coalesce the affected tissue can dry, crack, and curl. Drought stress causes the leaf margins to brown and curl inward; aronia is more drought-tolerant than many soft fruit plants but is not immune to wilting in a prolonged UK summer drought, particularly in containers or in light, sandy soils. Aronia is not significantly bothered by the cane diseases that affect its Rosaceae relatives such as raspberry and loganberry, which is one of the reasons it is considered an easy, low-maintenance shrub.

Q: What are the health benefits of aronia berries?

Aronia berries (Aronia melanocarpa) have attracted substantial research interest because they contain very high concentrations of anthocyanins (the dark pigment compounds responsible for the berries' near-black colour) and other polyphenol antioxidants, including proanthocyanidins and quercetin. In comparison studies, aronia berries consistently rank among the highest of any studied fruit for total antioxidant capacity, outperforming blueberry, cranberry, and elderberry. The astringency that makes the berries unpleasant to eat raw comes primarily from the very high concentration of proanthocyanidins (tannins), which are the same compounds responsible for some of the proposed health benefits. Research has investigated aronia juice and extracts in relation to cardiovascular health, blood pressure, blood glucose regulation, and anti-inflammatory effects; while results are promising, most studies are small and further clinical evidence is needed before specific health claims can be made. The berries are sold in the UK as dried berries, juice, powder, and capsule supplements, marketed primarily for their antioxidant content. As a culinary ingredient, aronia juice adds a deep colour and complex, tart flavour to smoothies, wine, and mixed-berry products.

Q: What do aronia berries taste like?

Aronia berries (Aronia melanocarpa) have a distinctive flavour that is deeply tart and very astringent when eaten raw, with an initial sweetness followed by a powerful, mouth-drying tannin sensation similar to very strong, over-brewed black tea or an unripe sloe berry. The 'choke' in chokeberry refers literally to the drying, puckering sensation the raw berries produce in the throat. Most people find the berries unpleasant to eat fresh in quantity, and they are best processed before eating: aronia juice (pressed and sweetened or mixed with apple juice) is more palatable; aronia jam is excellent, with a deep colour and complex, tart-sweet flavour; aronia wine has a deeply coloured, full-bodied character. In Scandinavia and Eastern Europe, where aronia is more widely cultivated than in the UK, aronia syrup (used as a cordial, flavouring, or mixer) and dried aronia berries (added to muesli and baked goods) are the most common preparations. The berries are high in natural sugars despite the astringency; the tannins mask the sweetness in the raw fruit.

Aronia (Aronia melanocarpa), also called black chokeberry, is a North American native shrub grown in UK gardens for its clusters of very dark, almost black berries in September, its outstanding autumn colour, and its extraordinary antioxidant content. It is among the hardiest and most disease-resistant fruit shrubs available for UK gardens, tolerating a wide range of conditions and requiring minimal intervention. When the leaves do curl, the cause is usually a minor aphid infestation on the spring growth, rather than anything more serious.

Aphids

Several aphid species, including the rose aphid (Macrosiphum rosae) and green apple aphid (Aphis pomi), can colonise the new spring growth of aronia, causing the leaves at the shoot tips to curl and distort. The infestation is usually brief; natural predators (ladybirds, lacewings, hoverfly larvae) typically establish on the colony within a few weeks and reduce populations significantly without intervention. Aronia is not as severely or as persistently affected by aphids as its Rosaceae relatives such as apple and pear; the problem usually resolves by June without lasting damage.

What to do

Check the shoot tips in spring. If the infestation is significant, apply insecticidal soap or neem oil to the affected tips and the undersides of the leaves. In most cases, leaving the infestation to natural predator control is sufficient; the plant is vigorous enough to shrug off a moderate spring aphid attack. Avoid broad-spectrum insecticides, which kill beneficial predators and disrupt the natural control that usually limits aphid populations on aronia.

Leaf spot

Leaf spot fungi, including Cercospora and Septoria-type species, can affect aronia in wet summers, producing small brown or purple spots on the leaf surface. In severe cases, multiple spots coalesce to cover large areas of the leaf; affected tissue dries, cracks, and curls. Premature leaf drop follows in a bad infection, weakening the plant and reducing the following year's berry production. Leaf spot on aronia is more common in overcrowded plantings with poor air circulation and in particularly wet UK summers.

What to do

Collect and destroy fallen leaves in autumn to reduce the overwintering spore load. Improve air circulation by removing the oldest canes from mature plants. Apply a copper-based fungicide spray in early spring and repeat every 14 days during prolonged wet periods if leaf spot has been a problem in previous years. Avoid overhead watering.

Drought stress

Aronia is more drought-tolerant than many soft fruit shrubs, but in a prolonged dry UK summer the leaves will curl inward at the margins and lose their glossy appearance, particularly on plants in containers or in light, sandy soil. The berries also suffer in severe drought, shrivelling before they reach full size. Aronia in the ground generally has sufficient rooting depth to find moisture in all but the most severe UK droughts; container-grown plants are more vulnerable.

What to do

Water plants in containers regularly throughout the growing season and thoroughly before drought periods. Apply a thick mulch of bark, wood chip, or garden compost around the base of plants in the ground in spring to retain soil moisture. Plants in the ground rarely need watering in a typical UK summer once established; the exception is a prolonged drought of more than 3 weeks without significant rainfall.

Frequently asked questions

Why are my aronia leaves curling?

Aronia (Aronia melanocarpa) leaves curl most commonly in the UK because of aphid infestation, leaf spot, or drought stress. Aronia is one of the hardiest and most disease-resistant fruit shrubs and serious problems are relatively rare. Aphids can colonise the new growth in spring, causing leaf curl at the shoot tips; natural predators usually control the infestation within a few weeks. Leaf spot fungi cause spots and leaf curl in wet summers. Drought stress causes the leaf margins to brown and curl inward.

Is aronia easy to grow in the UK?

Aronia (Aronia melanocarpa) is one of the easiest fruit shrubs to grow in the UK. It is extremely hardy (tolerating -30°C), adaptable to most soils from wet to moderately dry, self-fertile, and requires no hand-pollination or winter protection. It grows into a neat shrub of 1.5 to 2 metres, produces white flowers in spring attractive to pollinators, and provides outstanding autumn colour. Minimal pruning is needed. The main challenge is that the berries must be processed (as juice, jam, or wine) rather than eaten raw.

What are the health benefits of aronia berries?

Aronia berries contain very high concentrations of anthocyanins and other polyphenol antioxidants, consistently ranking among the highest of any studied fruit for total antioxidant capacity. Research has investigated aronia in relation to cardiovascular health, blood pressure, blood glucose regulation, and anti-inflammatory effects; results are promising but most studies are small and further clinical evidence is needed. Aronia is sold in the UK as dried berries, juice, powder, and capsule supplements.

What do aronia berries taste like?

Aronia berries are deeply tart and very astringent when eaten raw, with a powerful mouth-drying tannin sensation. The 'choke' in chokeberry refers literally to this puckering sensation. Most people find them unpleasant fresh in quantity; they are best processed as juice (mixed with apple juice), jam, or wine. In Scandinavia and Eastern Europe, aronia syrup and dried berries are common preparations. The berries are actually high in natural sugars despite the astringency; the tannins mask the sweetness.