Anchusa azurea, commonly called Italian bugloss, is one of the boldest blues in the cottage garden. It produces vivid gentian-blue flowers in dense racemes from late May through July, reaching 90 to 120 cm and attracting bees with remarkable reliability. The rough, bristly leaves and stout taproot give it a tough, self-sufficient character. In the UK it is a beloved border perennial, particularly in the classic cottage planting style, where varieties like 'Loddon Royalist' and 'Dropmore' have been grown for generations. Anchusa capensis, the Cape forget-me-not, is a closely related species commonly grown as a hardy annual in UK gardens, with a similar bright-blue flower and the same characteristic rough hairy texture on its leaves and stems.
Despite its tough appearance, anchusa has a handful of weaknesses that show up as curling, distorted, or discoloured leaves. Most are manageable once you can identify the cause. The two most common problems are aphid colonies on new growth and powdery mildew after first flowering, but red spider mite, drought stress, and the plant's own tendency to become woody and decline with age can produce similar symptoms.
Aphids: downward curl on new shoots
Aphids are the most common cause of curling on young anchusa leaves, particularly on the soft shoot tips that emerge in spring and after cutting back. Two species are regularly found on anchusa in UK gardens. The peach-potato aphid (Myzus persicae) is a pale green to pinkish insect that colonises many different plants and is one of the most widespread and damaging aphids in the UK garden. The black bean aphid (Aphis fabae) forms dense, highly visible jet-black colonies and is particularly common on anchusa from late spring through early summer. Both species feed by inserting stylets through the leaf tissue and extracting sap from the phloem, and both cause the same characteristic symptom: the leaves at the tips of growing shoots curl downward and inward, often trapping the colony inside the curl where it is protected from predators and from contact sprays.
Anchusa's rough, hairy leaves provide some protection against soft-bodied insects, and fully expanded adult leaves are less vulnerable than the tender new growth at the very tips of shoots. Colonies tend to concentrate where the leaf surface is softest: emerging leaves at the shoot apex, the undersides of the youngest expanded leaves, and the junction between leaf and stem. In warm, dry spells from May onwards, populations can build up very quickly because the warm conditions suppress natural predator activity initially while the aphids reproduce rapidly.
One characteristic sign of a well-established colony is the accumulation of honeydew, a sticky, sugary secretion excreted by the aphids as they feed. Honeydew coats the surfaces below the colony and rapidly becomes colonised by sooty mould, a black, superficial fungal growth that gives affected shoots a dark, dirty appearance. The sooty mould itself does not infect the plant tissue but it blocks light from reaching the leaf surface and is a reliable indicator that an aphid colony has been present for some time.
To deal with aphids on anchusa, begin by rubbing off colonies by hand on the most accessible shoots, or knock the insects off with a strong jet of water directed at the leaf undersides and shoot tips. Repeat this every two or three days until colony numbers fall. For persistent infestations, apply insecticidal soap or neem oil spray, coating the undersides of leaves and all shoot tips thoroughly. Because anchusa is a significant nectar source for bumblebees and solitary bees, avoid using systemic insecticides that persist in plant tissues and could harm pollinators. Allow beneficial insects, especially ladybirds and hoverfly larvae, to build up: once established, they are highly effective at reducing aphid numbers without any intervention.
Powdery mildew: white coating and upward curl
Powdery mildew is the disease most strongly associated with anchusa and is particularly common in the period immediately following first flowering. The pathogen responsible on anchusa is typically Erysiphe anchusae or a closely related species within the Erysiphales. It produces a white to pale grey, powdery coating on the upper surface of leaves, starting as scattered discrete patches and spreading to cover wide areas of the leaf surface as infection progresses. Affected leaves distort and curl upward around the infected areas, and the general appearance of the plant deteriorates markedly in a serious outbreak.
Anchusa azurea is particularly susceptible to powdery mildew because of the natural seasonality of its growth. The plant puts tremendous energy into the June to July flowering flush, and the foliage is often at its most stressed and least vigorous in the weeks immediately following. Warm days, cool nights, and dry soil conditions, which are not uncommon in UK summers from late June onwards, create exactly the conditions powdery mildew pathogens favour. Plants growing in sheltered positions with restricted airflow, or those growing in competition with tall neighbours that reduce air movement around the stems, are consistently worse affected than plants in open, breezy positions.
The standard and most effective response in UK cottage gardens is to cut the plant back hard after first flowering. Cutting the stems down to a basal mound of leaves removes all the infected growth in one step and stimulates the plant to produce a fresh flush of clean new foliage from the base. Many gardeners do this as a matter of routine regardless of mildew, because it also encourages a second, lighter flush of flowers in late summer and prevents the plant from setting excessive seed and exhausting itself. Following cutting back, apply a balanced granular or liquid fertiliser around the plant to support the new growth. Keep the root zone moist during dry spells by watering at the base, which also reduces the soil water stress that predisposes leaves to infection.
Where mildew appears on plants that have not yet finished their first flush of flowering, remove the worst affected leaves and improve airflow by clearing any overhanging or encroaching vegetation. A preventive or early-stage spray of dilute potassium bicarbonate or a copper-based fungicide can slow the spread if applied before the infection is widespread, but once mildew covers a large proportion of the leaf surface, cutting back is more effective and more practical than spraying.
Red spider mite: fine stippling in hot conditions
Red spider mite (Tetranychus urticae) becomes a significant problem on anchusa during prolonged hot, dry spells, which in UK gardens typically means July and August in a warm summer. Spider mite is not actually an insect but a tiny arachnid, barely visible to the naked eye. It feeds by puncturing individual plant cells on the underside of leaves and draining the contents, causing a characteristic symptom of fine, pale stippling or bronzing on the upper leaf surface. In a severe infestation, the underside of leaves becomes covered in fine silk webbing, and the leaves dry out, curl under at the edges, and may fall early.
Anchusa's rough leaf texture does not provide complete protection against spider mite, and the plants are vulnerable during the same dry summer conditions that also promote powdery mildew. The two problems can occur simultaneously on the same plant. To distinguish mite damage from mildew, check the underside of leaves with a hand lens: mite colonies appear as tiny moving dots, often reddish-orange or pale green, sometimes surrounded by fine webbing. There is no white powdery coating on the leaf surface as there is with mildew, and the bronzing or stippling on the upper surface of the leaf is quite different from the white coating of mildew.
Increase humidity around the plants by misting the foliage in the early morning during dry spells, as spider mite thrives in hot, dry, still air. A jet of water directed at leaf undersides knocks off mite populations and disrupts webbing. Biological control using predatory mites (Phytoseiulus persimilis) is available for controlled environments but impractical in the open garden. In very severe outbreaks, an oil-based or insecticidal soap spray applied to leaf undersides every three to five days can reduce the population, though good coverage of the leaf underside is essential for effectiveness.
Drought stress and cultural causes
Anchusa has a deep taproot that allows it to explore a large volume of soil for moisture, giving it reasonable drought tolerance once established. However, on very free-draining or shallow soils in a prolonged dry summer, the large rough leaves show clear signs of moisture stress. The leaf margins begin to curl inward along the length of the leaf, the surface becomes slightly dull, and the leaves may develop brown, crisping edges. Unlike aphid or mildew symptoms, drought-induced curl affects the whole plant more or less evenly rather than concentrating at shoot tips or on particular leaf surfaces, and it recovers quickly after rain or deep watering.
A separate cultural issue that produces similar symptoms to drought stress is the natural tendency of older anchusa plants to become woody at the base. Anchusa azurea is short-lived: in UK conditions it typically performs best in its first and second year from planting, then the root stock becomes increasingly woody and the plant produces progressively smaller, more congested, and more distorted new leaves. Self-seeded plants in fresh soil consistently outperform old woody specimens in the same bed. Plants that have not been cut back hard after flowering in previous years exhaust themselves more quickly and begin this decline sooner.
Septoria leaf spot, caused by Septoria fungi, occasionally affects anchusa, producing small brown spots with darker margins on older leaves. Severe Septoria infection can cause leaves to yellow around the spots and drop early, with some curling of affected tissue at the margins. The spots distinguish it clearly from mildew and aphid damage. Remove infected leaves, avoid overhead watering, and improve airflow around the plant.
Prevention and care through the season
Plant anchusa in sharply drained soil in full sun. It is one of those plants where drainage is more important than fertility: it tolerates poor, thin soil well but rots in heavy, wet conditions over winter, and wet clay kills it more reliably than cold. On heavier soils, incorporate grit or sharp sand generously into the planting area and consider raising the bed slightly to improve drainage.
Begin checking new shoot tips for aphid colonies from early May, before the main flush of growth in late spring. Colonies are much easier to deal with when they are small and confined to one or two shoot tips than when they have spread across many stems. Water at the base of the plant rather than overhead during dry spells: overhead watering wets the leaf surface and does not help the root zone as effectively, and wet leaf surfaces are more hospitable to fungal spores. Apply a layer of organic mulch around the base in late spring to conserve soil moisture through summer.
After the first flush of flowers in June to early July, cut the plant back hard, removing stems to a basal mound. This single action prevents mildew from taking hold on the post-flowering foliage, removes any aphid colonies on the upper stems, encourages a second lighter flowering in late summer, and extends the productive life of the plant by preventing premature exhaustion. Follow the cutback with a balanced feed and, on dry soils, a thorough watering. Allow a few self-seeded seedlings to develop nearby so that when the parent plant eventually declines, young replacements are already growing in.
Frequently asked questions
Why are my anchusa leaves curling?
Anchusa leaves most commonly curl because of aphid colonies on new shoot tips or because of powdery mildew infecting the leaf surface. Peach-potato aphid (Myzus persicae) and black bean aphid (Aphis fabae) both attack the soft new growth, causing downward curling and sticky honeydew deposits. Powdery mildew causes an upward curl and a white chalky coating, especially in dry conditions mid to late summer. Red spider mite in hot, dry weather can also cause fine stippling and downward curling of leaves, and drought stress produces inward marginal curling on the large rough leaves. Inspect the undersides of leaves and shoot tips to identify which problem you are dealing with.
Is anchusa susceptible to powdery mildew?
Yes. Anchusa azurea is particularly prone to powdery mildew, especially in the weeks following its early-summer flowering peak. The disease appears as a white powdery coating on the upper leaf surface and causes upward distortion and curling of affected leaves. Warm days and cool nights with dry soil encourage infection. The standard remedy in UK cottage gardens is to cut the plant back hard after the first flush of flowers finishes in early summer: this removes the infected growth and encourages a flush of clean, healthy new leaves from the base. Feeding the plant with a balanced fertiliser at the same time speeds up recovery.
What are the best varieties of Anchusa azurea for UK gardens?
The two most widely grown varieties of Anchusa azurea in UK cottage gardens are 'Loddon Royalist' and 'Dropmore'. 'Loddon Royalist' is the most popular, reaching around 90 cm and producing particularly intense gentian-blue flowers from June into July. It holds an RHS Award of Garden Merit and performs reliably in full sun with good drainage. 'Dropmore' is a slightly taller, older variety also bearing rich blue flowers and is valued for its reliability from seed. Both varieties are short-lived in UK gardens, often performing best in their first and second year before declining, but self-seeding freely in suitable conditions maintains a colony without the need to replant every year.
How do I treat aphids on anchusa?
For aphid colonies on anchusa, start by knocking the insects off with a strong jet of water directed at the undersides of young leaves and shoot tips. This alone can reduce colonies significantly. Apply insecticidal soap or a neem oil spray every three to five days until the colony is gone. Avoid broad-spectrum insecticides where possible, as anchusa is an important nectar source for bees, including bumblebees and solitary bees. Beneficial insects including ladybirds and hoverfly larvae will find established colonies and reduce them naturally once they are present in the garden. Monitor new shoot tips from May onwards, when aphid activity picks up rapidly in warmer weather.
Why is my anchusa declining after its first year?
Anchusa azurea is naturally short-lived, typically lasting two to four years in UK gardens before the root stock weakens and the plant produces progressively smaller, more distorted leaves and fewer flowers. Plants that are not cut back hard after first flowering become woody at the base and struggle to regenerate clean new growth. Poor drainage causing root rot over winter and heavy clay soils both shorten the plant's life. The most reliable approach is to cut back hard after first flowering each year, feed with a balanced fertiliser, and allow self-seeded seedlings to replace the oldest plants naturally. Anchusa self-seeds freely in open, well-drained soil and a colony renews itself with minimal intervention.