Why Are My Viscaria Leaves Curling?

Aphid infestation

Aphids are the most common pest on viscaria. The slightly sticky stems trap small insects naturally, but aphids colonise the shoot tips and the undersides of the narrow leaves with ease. Green aphids and black bean aphid are both found on viscaria. Aphid feeding causes the delicate leaves to curl, pucker, and distort, and heavy infestations on young plants can significantly shorten the flowering season. The slender stems and narrow leaves mean aphid damage is more visible on viscaria than on plants with larger, more substantial foliage.

What to do

• Check the shoot tips and the undersides of the narrow leaves regularly from early spring when aphid populations begin to build.
• Spray with insecticidal soap every four to five days for two to three weeks, covering all surfaces of the slender stems and narrow leaves.
• A gentle jet of water dislodges aphids effectively; the slender stems mean this must be done carefully to avoid damaging the plant.
• The flowers attract beneficial insects including hoverflies and lacewings: spray in the evening to avoid harming pollinators.

Overwatering

Overwatering is one of the most common causes of viscaria decline, particularly in containers or in heavy, poorly drained soil. Viscaria is adapted to dry, sunny conditions and the fine root system deteriorates rapidly in persistently wet compost. The narrow leaves yellow and curl, and the slender stems may collapse at the base. In a wet UK spring, viscaria in heavy clay or in containers on a fixed watering schedule is particularly at risk. The plant performs very poorly in waterlogged conditions and consistently outperforms in free-draining, relatively poor soil.

What to do

• Plant viscaria in well-drained, relatively poor soil. It does not need rich, heavily improved beds and actually performs better in leaner conditions.
• In containers, use a free-draining compost blended with perlite or grit and ensure excellent drainage holes.
• Do not water viscaria in the open ground unless there is a prolonged dry spell. In a typical UK spring, rainfall is usually sufficient.
• Allow the compost in containers to dry slightly between waterings rather than keeping it consistently moist.

Drought stress

Despite preferring free-draining conditions, viscaria still needs adequate moisture to flower well. Extended dry spells in late spring and early summer, when viscaria is at its peak, can cause the narrow leaves to curl and the plant to go to seed prematurely. Container plants are most at risk as their limited compost volume dries rapidly. Drought-stressed viscaria produces fewer and smaller flowers and sets seed more quickly, shortening the display significantly.

What to do

• Water viscaria during prolonged dry spells in spring, particularly during its main flowering period.
• Container-grown plants need regular checking: water when the compost has dried to 2 to 3 cm depth.
• Mulch around border plants with fine organic mulch to retain moisture during dry periods.

Heat stress

Like many hardy annuals, viscaria is a cool-season plant that performs best in the mild conditions of spring and early summer. Once consistent temperatures above 20 to 22 degrees Celsius arrive, the plants go to seed and their display ends. This natural decline is accelerated in very hot spells. The narrow leaves curl and the plant deteriorates rapidly once summer heat intensifies. This is normal behaviour rather than a problem.

What to do

• Accept that viscaria is a spring to early summer plant in the UK and plan successor sowings to fill the gap after it declines.
• Grow viscaria in a position that receives morning sun but some shade during the hottest part of the afternoon, which extends the season slightly.
• Allow self-seeding or make a repeat sowing in late summer or early autumn for plants that flower the following spring.

Powdery mildew

Powdery mildew occasionally affects viscaria as the plants are coming to the end of their season in warm, dry conditions. The narrow leaves develop a white powdery coating and curl slightly. It is most common on crowded plants with poor air circulation and on those that have been drought-stressed. By the time powdery mildew becomes obvious, viscaria is usually close to setting seed naturally.

What to do

• Thin direct-sown seedlings to 15 to 20 cm to improve air circulation.
• Remove badly affected plants and allow the remaining ones to set seed naturally for next year's display.
• Ensure adequate watering during dry periods to reduce susceptibility to powdery mildew.

Frequently asked questions

Why are my viscaria leaves curling?

Viscaria leaves curl most often from aphid infestation or overwatering. Aphids colonise the sticky stems and the undersides of the narrow, lance-shaped leaves, causing them to curl and distort. Overwatering in poorly drained soil causes yellowing and curling as the fine root system deteriorates, since viscaria is adapted to dry, free-draining conditions.

What is viscaria?

Viscaria oculata (also known as Silene coeli-rosa or rose of heaven) is a hardy annual grown for its delicate, five-petalled flowers in shades of pink, magenta, white, and red, each with a contrasting darker eye. The slender, slightly sticky stems and narrow leaves give the plant a light, airy quality, making it ideal for mixed annual sowings, wildflower meadows, and cutting gardens.

When should I sow viscaria?

Sow viscaria direct in its final position in autumn for a spring to early summer display, or in early spring from February to April. It is a hardy annual that germinates readily in cool conditions. Autumn sowings produce the most floriferous plants. Thin to 15 to 20 cm apart once large enough to handle. Viscaria dislikes root disturbance and is best direct sown rather than transplanted.

Does viscaria self-seed?

Yes, viscaria self-seeds freely if the plants are allowed to shed their seed before they are removed. The seeds germinate in autumn on bare soil and overwinter as small seedlings. In established gardens, viscaria perpetuates itself from year to year without any additional sowing effort. Allow a few plants to set seed each year rather than deadheading everything.