About Arabis (Rock Cress)
Arabis, commonly known as rock cress, is a low-growing mat-forming perennial in the family Brassicaceae. The species you are most likely growing in a UK garden is Arabis caucasica, the Caucasian rock cress, which produces masses of small four-petalled white flowers from March to May and grows to around 20 cm tall. It is completely hardy throughout the UK and is the plant most often sold in British garden centres under the name "arabis." Arabis alpina, the Alpine rock cress, is closely related and behaves in much the same way. Arabis ferdinandi-coburgii 'Variegata' is a more compact form (around 10 cm) grown mainly for its creamy-white edged leaves and year-round foliage interest.
Arabis is native to rocky mountain areas of southern Europe, the Caucasus, and the Middle East. In the wild it colonises well-drained, often alkaline, stony soils in full sun, and that tells you everything you need to know about what it wants in your garden: brilliant drainage, a sunny spot, and thin, slightly gritty soil. Rich, damp, or waterlogged conditions are the enemy.
In UK gardens, Arabis caucasica is one of the five or six classic spring rockery and wall plants. It cascades beautifully over dry stone walls, naturalises in the mortar between stones, and works as ground cover on sunny sunny banks. The most celebrated use is the classic spring trio of Arabis (white), Aubrieta (purple), and Aurinia saxatilis (golden yellow), which together create one of the most vivid seasonal displays in the British garden. The white flowers are also excellent early nectar for bees and other pollinators emerging in March and April.
Why Are Your Arabis Leaves Curling?
The two most common causes of curling leaves on Arabis are flea beetle damage and grey mould building up inside congested, unpruned mats. Both are preventable with good cultural practice. Several secondary causes are also worth ruling out depending on the time of year and conditions.
Cause 1: Flea Beetle Damage
Arabis belongs to the Brassicaceae family, and like all members of that family it is susceptible to flea beetles (Phyllotreta species). These tiny, metallic, jumping beetles chew distinctive small circular holes through the leaves, giving the foliage a shot-through appearance. As the damage accumulates, the leaf margins curl and the leaves look tattered and sorry.
Flea beetles are most damaging on soft new growth. This makes them particularly problematic on Arabis in late spring and early summer, when fresh foliage emerges after the annual post-flowering cut-back. A warm, dry spring encourages the beetles; moist, fast-growing conditions give the plant a better chance of outrunning the damage.
Arabis shares this vulnerability with its rockery neighbours Aubrieta and Aurinia, as well as with cabbage-family vegetables. If you grow brassicas nearby you may find flea beetles moving between them.
What to do: Cover fresh growth after the cut-back with fine insect mesh until the new leaves have hardened off. Water the plant at the roots during dry spells to reduce stress and encourage faster regrowth. Treat with insecticidal soap if populations are high, applying in the evening to avoid harming pollinators. Established mats usually outgrow the damage each year; the problem is most serious on young plants or plants freshly divided and replanted.
Cause 2: Grey Mould on Congested or Unpruned Mats
Arabis builds dense, hairy mats over time. If the plant is never cut back after flowering, the old flowered stems become woody and the centre of the mat becomes a trap for moisture, dead leaves, and debris. Over winter, or during wet spells, Botrytis cinerea (grey mould) takes hold in this compressed, poorly ventilated core. The inner leaves collapse, brown, and curl inward. In damp conditions you may see a fuzzy greyish coating.
This is the same pattern that affects Aubrieta and other low mat-forming rockery plants. The remedy is identical: cut the entire mat back hard immediately after flowering, to within a few centimetres of the ground. This is not optional maintenance; it is the single most important annual task for keeping Arabis healthy. An unpruned plant becomes woody, bare in the centre, and increasingly prone to disease within two or three years.
One critical timing note: cut back in late spring or early summer, straight after the flowers finish. Do not cut back in autumn. The plant needs its full complement of foliage going into the colder months. An autumn-pruned Arabis can struggle to regenerate in spring.
What to do: If you find grey mould already present, cut back any affected growth immediately and remove it from the garden (do not compost it). Then improve air circulation by pruning the mat as described. If the central crown is badly rotted, the plant may not recover; take cuttings from any healthy outer shoots before removing the parent plant. Ensure the soil drains freely: add grit if needed. Avoid overhead watering.
Other Causes to Consider
Powdery mildew can affect Arabis in dry summers, particularly on plants in warm, sheltered spots with poor air movement. The characteristic white powdery coating on the leaf surface is accompanied by leaf curling and yellowing. Improve air circulation by pruning. Water at the root rather than overhead. Mildew rarely kills Arabis outright but weakens it over successive seasons.
Drought stress causes leaf margin curling, particularly in prolonged dry spells. Arabis is more drought-tolerant than most plants (the hairy leaves reduce water loss), but it is not immune. Plants on very poor, shallow soils over rubble or concrete are most vulnerable. Water at the root during extended dry periods. Do not mulch heavily; Arabis dislikes organic mulch sitting against its stems.
Aphids cluster on shoot tips in spring, causing distorted, curled soft growth. Colonies are visible to the naked eye. Knock them off with a strong jet of water or apply insecticidal soap. Avoid broad-spectrum insecticides in spring when Arabis is in flower and pollinators are visiting.
White blister rust (Albugo candida) occasionally affects Brassicaceae family members including Arabis, producing pale, blister-like pustules on the undersides of leaves and distorted growth. It is uncommon on rock cress but worth checking if the symptoms do not match the main causes above.
Vine weevil grubs can be a serious problem on containerised Arabis. The grubs eat roots below the soil surface; the first visible sign is often a plant that suddenly wilts despite adequate watering. Check the compost for the characteristic C-shaped cream grubs and treat with a nematode drench in late summer or early autumn.
Prevention: Keeping Arabis Healthy Long-Term
Most problems with Arabis trace back to one or more of the same basic mistakes: wrong site, no annual pruning, and neglected congestion. Get those three things right and the plant is remarkably trouble-free.
Plant in full sun in very free-draining soil. If your soil is heavy clay, incorporate generous quantities of sharp grit and consider raised beds or a dry stone wall planting instead of the open border. Arabis genuinely thrives in poor, lean conditions. Fertile, damp soil produces lush, disease-prone growth and a short-lived plant.
Cut back hard every single year after flowering. No exceptions. Shear the whole mat to within a few centimetres of the ground as soon as the flowers finish, typically in May or June. The plant will regenerate vigorously and the fresh foliage makes excellent ground cover through the summer and autumn.
Protect emerging new growth after the cut-back with fine insect mesh if flea beetles are a recurring problem. Water during the period of regrowth to support the plant.
Divide or replace congested clumps every three to four years. Arabis is easy to propagate from cuttings taken in summer after the annual cut-back: take short, non-flowering shoots, strip the lower leaves, and root in a gritty cutting compost. This gives you a constant supply of young, vigorous plants and is far more reliable than seed propagation for named varieties such as 'Flore Pleno' and 'Rosabella', which may not come true from seed.
Frequently Asked Questions
When and how should I cut back Arabis after flowering?
Cut Arabis back hard immediately after flowering finishes, typically in May or early June. Use shears or scissors to trim the whole mat to within a few centimetres of the ground. This removes the old flowered stems, prevents the centre from becoming woody and bare, dramatically improves air circulation, and reduces the risk of grey mould the following winter. Do not cut back in autumn; the plant needs its foliage going into the colder months. This single annual task is the most important thing you can do to keep rock cress looking good year after year.
What is the classic UK spring rockery trio and how does Arabis fit in?
The classic combination is Arabis caucasica (white), Aubrieta (purple or mauve), and Aurinia saxatilis (golden yellow). Planted together in a sunny rock garden or cascading over a dry stone wall, they flower simultaneously in March, April, and May, creating a vivid three-colour display that has been a staple of British spring gardens for generations. All three require the same conditions: full sun, very free-draining slightly alkaline soil, and a hard cut-back after flowering. They also share common pests, particularly flea beetles, which move freely between them.
How do I tell flea beetle damage from grey mould on my Arabis?
Flea beetle damage shows up as small, neat shot-holes scattered across the leaf surface, often with the leaf margins curling and looking ragged. You may see tiny metallic jumping beetles if you disturb the foliage. Grey mould (Botrytis) starts in the dense centre of an unpruned mat; the inner leaves collapse, go brown, and curl inward, and you may see a greyish fuzzy coating in damp conditions. Flea beetles are most active on fresh new growth in spring and early summer. Grey mould tends to appear after winter or in persistently wet weather. Both problems are made worse by congested, unpruned mats.
Can I grow Arabis in a container?
Yes, but free drainage is critical. Use a loam-based compost mixed with plenty of grit or perlite, and ensure the pot has adequate drainage holes. In containers, vine weevil grubs are a particular risk; they eat the roots invisibly and the first sign is often a plant that suddenly wilts or collapses despite adequate watering. Check the compost for the characteristic C-shaped cream grubs and treat with a nematode drench in late summer or early autumn. Containerised Arabis will also dry out faster in summer, so check soil moisture during prolonged dry spells and water at the base.
Which Arabis varieties are best for UK gardens?
Arabis caucasica (Caucasian rock cress) is the standard choice, completely hardy throughout the UK and widely available in garden centres. 'Flore Pleno' has attractive double white flowers that last slightly longer than the single form. 'Rosabella' produces soft pink flowers and is slightly less vigorous, making it useful in smaller spaces. Arabis ferdinandi-coburgii 'Variegata' is grown mainly for its neat, creamy-white edged leaves and is very compact at around 10 cm; it provides good year-round foliage interest even when not in flower. Arabis alpina (Alpine rock cress) is closely related and behaves similarly in cultivation.