Cynoglossum amabile, known as Chinese forget-me-not or hound's tongue, is a biennial or short-lived annual in the borage family (Boraginaceae) grown for its intense sky-blue flowers that appear from June to August. The soft, grey-green, hairy leaves and branching stems reach 45 to 60 cm, and the blooms are considerably larger and more saturated in colour than true forget-me-nots. Cynoglossum officinale, the common hound's tongue, is a UK native biennial of chalk grassland, scrub, and disturbed limestone ground that produces dull reddish-purple flowers and grows taller still. Both species develop problems with curling leaves at some point in the growing season, almost always because of aphids, powdery mildew, or the dry summer conditions that encourage both.
Why cynoglossum leaves curl
Cynoglossum's soft, hairy leaf texture gives it some incidental textural resistance to insect colonisation but does not prevent aphids from reaching the soft growing points where new leaves are forming. The plant's membership of the Boraginaceae family is the most important factor in predicting its vulnerabilities: the entire family shares a susceptibility to powdery mildew fungi, making cynoglossum behave more like borage or anchusa in this respect than like other blue-flowered annuals such as nigella or love-in-a-mist. Understanding the family context helps narrow down a diagnosis quickly. Aphid infestation and powdery mildew account for the great majority of cases of cynoglossum leaf curling, but flea beetles in hot dry spells, slugs on spring seedlings, drought stress, and waterlogged roots are all worth checking against the symptoms you are seeing.
Cause 1: Aphids (peach-potato aphid, Myzus persicae, and related species)
The peach-potato aphid (Myzus persicae) is one of the most generalist and damaging aphid species in UK gardens and is frequently found on cynoglossum, particularly during warm, dry spells when the colonies spread rapidly. Colonies establish on the shoot tips and soft growing points, where the plant tissue is youngest and most nutritious. The feeding causes the cells of the surrounding leaves to develop unevenly, pulling the new foliage downward into a characteristic inward curl that shelters the colony from both weather and predators. Sticky honeydew coats the foliage below the colony, and black sooty mould soon develops on the honeydew, reducing the plant's capacity to photosynthesise.
Cynoglossum's hairy leaves provide some protection to the tougher, more mature lower foliage, but aphids routinely bypass this by targeting only the soft, hairless tissue at the growing tips. Colonies are typically worst in warm, dry weather from May onward and often self-regulate as ladybirds, lacewing larvae, parasitic wasps, and other natural predators locate and exploit the food source. A colony that appears alarming in May will often be largely cleared by natural predation within three to four weeks if no insecticide is applied.
How to fix aphid infestations on cynoglossum
Begin with the least disruptive intervention. Pinch out the heavily colonised shoot tips and discard them away from the garden to remove the bulk of the colony instantly. Blast the remaining aphids off with a firm jet of water directed at the stem tips, repeating every two to three days. For persistent colonies on plants where the appearance matters, apply insecticidal soap or a diluted neem oil solution directly to the infested growing points, directing the spray into the curled leaves where aphids shelter. Avoid broad-spectrum or systemic insecticides: they kill the parasitic wasps and ladybirds that are building up in response to the colony and will prolong the infestation over the long run. Healthy colonies of natural predators establish most quickly when no insecticide is used.
Cause 2: Powdery mildew (Erysiphe or related Boraginaceae-family species)
Powdery mildew is the defining disease vulnerability of the Boraginaceae family. Cynoglossum, borage, anchusa, comfrey, and forget-me-nots are all susceptible to closely related powdery mildew fungi that produce the characteristic grey-white, floury coating on the leaf surface, accompanied by upward curling of affected leaves and general yellowing. On cynoglossum, the condition typically appears from midsummer onward, becoming increasingly prominent as the season moves into late July and August.
The fungus does not require wet conditions to spread. It thrives when warm, dry days produce a degree of moisture stress in the plant, making the leaf surface vulnerable, while cool, humid nights allow the fungal spores to germinate and extend the mycelium across the foliage. Plants growing in crowded conditions, in partial shade, or in dry soil are significantly more susceptible than well-spaced plants in full sun with consistent moisture. Cutting back affected stems to basal growth, rather than treating only the symptoms on existing foliage, often produces a worthwhile flush of fresher, less susceptible regrowth in late summer.
How to fix powdery mildew on cynoglossum
Remove and bin the most heavily affected leaves and stems at the first sign of infection to reduce the spore load on the plant and in the surrounding air. Apply neem oil or a potassium bicarbonate spray to both surfaces of the remaining foliage, covering the underside as well as the top, and repeat at weekly intervals until the symptoms stop progressing. Water consistently at the base of the plant during dry spells: mildew severity is closely linked to water stress at the roots, and a well-watered plant in dry weather is noticeably more resistant than a drought-stressed one. Where a plant is badly infected in mid to late summer and beginning to decline naturally toward the end of its life cycle, cut it back hard and allow it to set seed if self-seeding in the garden is welcome.
Other causes of cynoglossum leaf curling
Flea beetles. In hot, dry conditions, flea beetles create small, regular, round holes in cynoglossum leaves, particularly on seedlings and young plants. The damage is characteristic: neat circular holes punched through the leaf surface rather than the ragged irregular grazing of slugs. Surrounding leaf tissue can curl and distort as a stress response to the cell damage. The beetles themselves are tiny, shiny, and jump when disturbed. Keeping the soil consistently moist during dry spells reduces flea beetle damage significantly, as the beetles are most active when conditions are hot and arid. Young seedlings are at most risk; established plants generally tolerate moderate damage without serious long-term harm.
Slugs and snails on seedlings. Slugs represent one of the most significant threats to cynoglossum at the germination and seedling stage in spring. They can consume a newly emerged seedling overnight, leaving nothing but a slime trail, and surviving seedlings can remain curled, stunted, and stressed from cell damage for weeks afterward. Protect newly sown areas and transplanted seedlings with organic slug pellets scattered around (not on) the plants, sharp grit or crushed eggshell as a physical barrier, or regular evening patrols and hand removal. Water in the mornings to allow the soil surface to dry before nightfall, when slug activity peaks.
Drought stress. Cynoglossum has a fibrous root system that performs adequately in well-drained conditions but is not particularly drought-tolerant compared to deep-rooted perennials. In a prolonged dry period, the leaves wilt and curl as the plant conserves water, and the overall appearance becomes limp and dull rather than the upright, healthy growth of a well-watered plant. This stress response is distinct from aphid curling (no colonies present) and mildew curl (no white coating), and the plant typically recovers promptly once watering resumes. Water at the base of the plant rather than overhead, and apply a mulch around (not touching) the stem base to retain moisture during dry spells.
Overwatering and poor drainage. Cynoglossum is intolerant of waterlogged or persistently wet soil. Overwatering or planting in heavy clay that holds water causes yellowing of the lower leaves, softening and rotting at the stem base, and a general collapse of the plant that can initially look like drought stress or nutrient deficiency. Check the soil: if it is consistently wet and cold to the touch at root depth, drainage is the problem rather than any pest or disease. Grow cynoglossum in a well-drained position, incorporating grit into heavy soils before planting, and allow the soil surface to dry slightly between waterings once plants are established.
Prevention
- Sow in a well-drained position in full sun. Cynoglossum performs best and is least susceptible to both powdery mildew and root problems when grown in freely draining soil with good light. Heavy or waterlogged soils cause root rot; shade promotes mildew and reduces vigour.
- Protect seedlings from slugs from the moment of germination. Slug damage at the seedling stage is the most common cause of cynoglossum failure in UK gardens, particularly in spring when slug populations are at their highest and seedlings are at their most tender. Organic pellets, grit barriers, and morning watering all reduce losses.
- Thin to good spacing for air circulation. Seedlings grown in clusters or transplanted too close together develop powdery mildew significantly earlier and more severely than well-spaced plants. Allow at least 25 to 30 cm between plants to ensure good airflow around the foliage.
- Water at the base, not overhead. Overhead watering wets the foliage, creates the humid leaf surface that powdery mildew spores need to germinate, and increases the risk of botrytis and other fungal issues in wet weather. A watering can or drip line directed at the root zone keeps the foliage dry and the soil consistently moist.
- Grow in an open position away from fences and walls. Enclosed positions reduce air movement, increase humidity around the foliage, and create the still-air conditions that powdery mildew favours. An open border or bed in full sun with good air circulation from all sides produces the healthiest plants.
- Allow natural predators to build up before intervening. Aphid colonies on cynoglossum typically attract ladybirds, parasitic wasps, and lacewing larvae within two to three weeks of establishment. Waiting and watching before applying any treatment often results in the colony being cleared naturally, with no damage to the beneficial insect population that will protect the garden through the rest of the season.
Frequently asked questions
Why are my cynoglossum leaves curling?
Cynoglossum leaves curl most commonly because of peach-potato aphid infestation or powdery mildew. Aphids (Myzus persicae) form colonies on the shoot tips and soft growing points, causing the new leaves to curl downward around the colony, accompanied by sticky honeydew deposits and sooty mould. Powdery mildew, to which all Boraginaceae family plants are susceptible, produces a white floury coating alongside leaf curl and yellowing, and is most severe in dry conditions during mid to late summer. Flea beetles in hot dry spells create small round holes in leaves causing wilting and distortion. Slugs damage young seedlings in spring. Drought stress on the fibrous root system causes wilting and curling. Overwatering causes yellowing and rotting at the base.
What is eating my cynoglossum seedlings?
The most likely culprits on cynoglossum seedlings in a UK garden are slugs and snails, especially in spring when germinating plants are at their most vulnerable. Slugs leave irregular, ragged holes in the soft leaves, often consuming seedlings entirely overnight. Surviving seedlings can look curled and stunted from the stress of the damage. Flea beetles are a secondary threat in hot, dry conditions: they leave small, regular, round holes punched through the leaf surface rather than the ragged grazing of slugs, and the surrounding leaf tissue may curl and distort as a response. Protect seedlings with a ring of organic slug pellets, a physical barrier of sharp grit around the planting area, or regular evening patrols, and water in the mornings rather than evenings to reduce overnight slug activity when the soil surface is at its most attractive.
Why does my cynoglossum have white powder on the leaves?
White powdery coating on cynoglossum leaves is caused by powdery mildew, a fungal disease to which all members of the Boraginaceae family are susceptible. Cynoglossum shares this vulnerability with borage, anchusa, comfrey, and forget-me-nots. The fungus thrives in dry conditions when the plant is slightly water-stressed, particularly from midsummer onward as the season progresses. Affected leaves develop a grey-white floury coating, curl at the margins, and may yellow and drop. Cutting back affected stems to basal growth often prompts fresher, cleaner regrowth. Apply neem oil or a potassium bicarbonate spray at the first sign of infection, ensure plants have adequate moisture at the roots, and improve air circulation by thinning any crowded plantings.
Is cynoglossum amabile easy to grow from seed in the UK?
Yes. Cynoglossum amabile (Chinese forget-me-not) is very easy to grow from seed in the UK and is best treated as a biennial: sow outdoors in summer (June to August) for flowering plants the following May to July. It germinates readily without heat, produces an overwintering rosette of soft grey-green hairy leaves, then flowers freely in its second year with intense sky-blue blooms that are considerably larger than true forget-me-nots. It self-seeds in suitable, well-drained conditions, which means a population can persist in the garden once established. It tolerates most soils but performs best in a freely draining position in full sun. Overcrowded seedlings are more susceptible to powdery mildew, so thin to at least 25 to 30 cm apart for best results.
What is the difference between cynoglossum and forget-me-not?
Cynoglossum amabile (Chinese forget-me-not) and Myosotis (true forget-me-not) are both members of the Boraginaceae family and produce blue flowers with a similar five-petalled structure, but they differ significantly in scale and habit. Cynoglossum amabile is substantially larger, typically reaching 45 to 60 cm tall, with broader, softly hairy grey-green leaves and flowers that, while individually similar to forget-me-nots, are carried on taller, more branching stems and appear later in the season (June to August rather than the April to May peak of Myosotis). The flowers of cynoglossum are also typically a more saturated, intense sky blue. Cynoglossum officinale, the common hound's tongue and a UK native biennial of chalk grassland and scrub, is taller still (to 90 cm) and produces dull reddish-purple flowers rather than blue; it is less commonly grown ornamentally but is a valuable wildlife plant, particularly for seed-eating birds and specialist invertebrates.