<em>Arabis</em>, corbeille d'argent: planting and care

Description and botany

Arabis, also known as rock cress or silver rock cress, is a perennial plant belonging to family Brassicaceae or crucifers such as cabbages.

Genus Arabis includes nearly 120 species, mainly evergreen perennials native to mountain regions and rocky slopes of Europe, notably the Caucasus, Asia and North America. They grow wild in stony soils as well as in sandy deserts of Arabia.

The most widely cultivated species is Arabis caucasica, Caucasian rock cress or silver rock cress. It is available in many cultivars. Also fairly common is Arabis blepharophylla, a less hardy species suited to mild climates, and Arabis ferdinandi-coburgii, with a lower habit that makes an excellent groundcover.

With a sprawling or erect habit, Arabis spreads easily by rootstocks to form cushions of persistent rosettes. Its trailing shoots root on contact with soil while branching theoretically without limit; habit is nonetheless not invasive.

With growth ranging from fairly slow to fast depending on species, it forms a dense groundcover not exceeding 30 cm in height, with a minimum spread of about 20 cm.

Arabis alpina – botanical illustration

From a dense or looser rosette emerge simple leaves, dentate or entire, elliptical to ovate, lanceolate and recurved according to species. They measure 1 to 5 cm long and are sometimes glossy and leathery or conversely covered with a velvet that reddens in cold. They form a thick tapetum of grey-green, glossy green, dark green or grey-green leaves marginate with cream-white. Some Caucasian rock cresses display light grey foliage that has earned them the name “silver rock cress”.

Arabis has a light, generous and eye-catching spring flowering. From these densely leafy cushions, a multitude of small, fresh-coloured flowers emerge from April to June, sometimes earlier if temperatures are mild. Each rosette produces a flowering stem bearing at its tip light clusters of flowers 3 to 8 cm long held above foliage.

Flowers about 1 to 2 cm in diameter, grouped in compact spikes, are made up of four rounded petals arranged in a cross. Flowers are single, sometimes fully double and generally pure white or pale pink to purple centred on a pale yellow heart: they combine simplicity with abundant flowering.

Slightly fragrant in some cases, they attract bees and butterflies for more than a month throughout spring.

Arabis is truly an easy and tolerant perennial to grow. Most often very hardy (from -15°C to -25°C), it can be cultivated in all regions.

Although it shows a clear preference for dry soils, even poor, rocky or gravelly, it will grow in richer, humus-bearing soil. Rock cress thrives in sun and never fears drought. It does, however, dislike soils that are too compact or too wet.

With its simple flowers, Arabis brings a rustic touch to all natural-style gardens.

Some Arabis flowers: A. caucasica ‘Pinkie’, A. caucasica ‘Snowcap’, A. alpina subsp. caucasica ‘Roselite’ and A. caucasica ‘Plena’

Some Arabis foliage: Arabis ferdinandi coburgii ‘Variegata’, Arabis caucasica ‘Pinkie’, Arabis alpina ssp caucasica ‘Variegata’, Arabis ferdinandi coburgii ‘Old Gold’

Main species and varieties

Most popular

Our favourites

Arabis alpina subsp. caucasica Snowcap

A particularly floriferous cultivar with early, slightly scented flowering, covering the whole plant. With its compact habit, it slips everywhere to cover low walls, climb embankments and carpet the base of hedges.

• Flowering time May to July
• Height at maturity 15 cm

See the product sheet

Arabis blepharophylla

Its small deep-pink flowers cover a cushion of evergreen leaves. Moderately hardy, it is grown in regions with mild, not very humid winters.

• Flowering time May to July
• Height at maturity 15 cm

See the product sheet

Arabis ferdinandi coburgii Variegata

It forms a tapetum of dark glossy evergreen leaves marginate with cream and topped by white flowers.

• Flowering time June, July
• Height at maturity 10 cm

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Arabis alpina subsp. caucasica Pinkie

A cultivar selected for the colour of its flowers. It forms a very effective spreading groundcover, ideal at borders, in a flowering paved area or crowning a low wall.

• Flowering time May to July
• Height at maturity 15 cm

See the product sheet

Arabis x suendermannii

A fairly rare rockery plant, particularly decorative with its tiny evergreen, leathery foliage and its scented spring flowering, which readily reblooms in autumn. It is ideal for emphasising a flight of steps, the edge of a border or a gravel path.

• Flowering time May to November
• Height at maturity 10 cm

See the product sheet

Arabis ferdinandi coburgii Old Gold

A species of silver basket with variegated foliage. Perfect as groundcover, on borders, in paving, atop a low wall or on a rocky bank.

• Flowering time June, July
• Height at maturity 15 cm

See the product sheet

Planting

Where to plant Arabis or rock cress

Arabis tolerates cold and drought very well: most species are hardy down to -20°C. It therefore establishes itself throughout France.

As quintessential rockery plant, rock cress likes sun and free-draining soil.

Although it prefers fairly undemanding growing conditions — dry, stony, well-drained soil — it will adapt to richer, cooler, humus-bearing soil, but will tend to spread more, losing some compactness. It also copes very well with sandy soils of seaside gardens.

It cannot tolerate excessively compact soil or soil that remains too wet in winter.

It is easy to grow in full sun but will tolerate partial shade: foliage will develop there at expense of flowering.

Arabis is an excellent groundcover, capable of quickly occupying a large area! Its propensity to suppress weed emergence makes it an excellent alternative to lawn in dry ground. Mat-forming by nature, it needs space and may tend to smother more delicate neighbouring plants.

Silver Basket always adds lightness to compositions it inhabits.

If Arabis is the quintessential plant for naturalistic rock gardens (unsuited to formal rockeries), it also makes an excellent groundcover to casually carpet base of bushes or hedges, scallop edge of a border or path, run freely through paving, cascade from top of a low wall or dry bank, and flower a pot or a planter.

When to plant Arabis or Silver Baskets

Arabis are best planted in spring, from March to May in colder regions once risk of frost has passed, or from September to November in southern France.

How to plant Arabis or Silver Basket

In open ground

Arabis or rock cresses are perennials that benefit from being planted at 7 to 9 plants per m2, spaced about 30 cm apart to allow stems to stretch freely and to cover soil effectively. In heavy soils, add a good amount of coarse sand or gravel to improve drainage: it grows very well in sand!

• Work soil well
• Dig hole 2 to 3 times wider than bucket
• Lay gravel at base of hole
• Plant without burying collar, covering it with 3 cm of soil
• Firm down lightly
• Water generously at planting

Plant Arabis or Silver Basket in a pot

Plant alone or in combination; even rock cress may invade or even smother other plants. Choose a container wider than it is deep.

• Spread a good draining layer (grit or clay pebbles) at base of pot
• Plant in a mix of garden soil and leaf mould compost with fine sand in equal parts
• Water regularly

Arabis blepharophylla

Care, pruning and maintenance of Arabis

Rock cress is a truly undemanding perennial, tolerant of drought, it requires almost no watering. In the first spring, give it regular waterings but do not overwater. Once well rooted, it will no longer need any water.

In a pot, soil dries out faster than in the open ground, water generously during growth, allowing the growing medium to dry well between waterings. Water sparingly in winter.

Each year in autumn, add a little compost if necessary to keep the plant vigorous.

In winter, protect less hardy species (Arabis blepharophylla) from cold with a mulch of dried leaves or straw.

Remove faded flowers as they appear.

Pruning is not necessary. You may simply need, after flowering, to cut clumps back by half to maintain compact growth.

Potential diseases and pests

Arabis is not very prone to diseases. White rust can attack foliage. Water without wetting foliage. Cut away and destroy diseased leaves, then treat with sprays of nettle manure or horsetail manure.

Shoots can be attacked by the Arabis gall midge or cabbage midge, which causes galls deforming flower stems; cut off and burn them. Apply sprays based on natural pyrethrum.

Arabis caucasica ‘Alabaster’

Propagation

If sowing Arabis is possible in autumn under cold frame, propagation by cuttings and division remain the simplest and quickest methods.

When and how to take herbaceous cuttings of Arabis

• Take tips of lateral shoots in June
• Remove lower leaves
• Plant them in pots in a light mix of turf and sand
• Place cuttings in shade
• Water cuttings regularly
• Overwinter them frost-free under cold frame
• Pot on into a larger pot when new shoots appear
• Plant out in autumn or following spring

Division

Clump division is easiest way to multiply Arabis. Carry out in autumn, after flowering.

• Using fork or spade, lift clump and remove young rosettes with roots located at edge of clump
• Plant immediately and water until established

Associate

With its evergreen foliage and fresh-toned flowers, Arabis is indispensable in dry gardens, in mineral landscapes and in the naturalistic holiday gardens of seaside, alpine or Mediterranean areas where it forms stunning year-round low-maintenance cushions.

Arabis scopoliana in rockery (photo Michael Wolf)

Thanks to its delicate habit, it complements spring scenes with charm by adding volume and light, notably in white/silver or white/pink schemes. It is easy to harmonise with biennials, early bulbs and other early perennials.

An idea for a combination on a low wall: Bergenia purpurescens and Arabis caucasica ‘Snowcap’

It will green rockeries alongside Alyssums, Aubrietas and campanulas.

In beds or borders, its versatile size allows it to be slipped between spring-flowering bulbs such as Muscari, Narcissi, Tulips, scillas…

An idea for a border combination: Carex oshimensis ‘Everest’, Tulip ‘Calgary’, white Bellis perennis, white Erysimum, Hyacinth ‘Madame Sophie’ and Arabis caucasica like ‘Snowcap’ (photo Jan Sølve Borlaug)

To be paired with other rockery perennials such as small sedums, Iberis, moss phlox or aubrietas, or used as a groundcover for bulbous plants.

In pots or window boxes, it will accompany daisies, forget-me-nots and early tulips.