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

Description and botany

The Arabis, also known as rock cress or Silver Basket, is a perennial belonging to the family Brassicaceae or Crucifers, like cabbages.

The genus Arabis includes nearly 120 species, mainly evergreen perennials native to mountainous regions and rocky slopes of Europe, notably the Caucasus, to Asia and North America. They grow naturally in stony soils as well as in sands of Arabian deserts.

Most widely cultivated species is Arabis caucasica, Caucasus rock cress or Silver Basket. It occurs in numerous cultivars. Also encountered fairly frequently are Arabis blepharophylla, a less hardy species to be reserved for mild climates, and Arabis ferdinandi-coburgii, lower in habit and an excellent groundcover.

With a spreading or erect habit, Arabis easily spreads by rootstocks to form cushions of evergreen rosettes. Its creeping shoots root at soil contact while branching in theory without limit, its character however not being invasive.

With growth ranging from fairly slow to rapid depending on species, it forms a dense groundcover not exceeding 30 cm in height, with a minimum spread of 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 from 1 to 5 cm long and are sometimes glossy and leathery or, on the contrary, covered with a velvety hair that flushes purple in cold. They form a thick tapetum in shades of grey-green, glossy green, dark green or grey-green marginate with cream-white. Some Caucasus rock cresses display pale grey foliage that earns them the name “Silver Basket”.

Arabis has a light, generous and eye-catching spring flowering. From these densely leafy cushions emerge a multitude of small fresh-coloured flowers from April to June, sometimes earlier if temperatures are mild. Each rosette produces a flowering stalk bearing at its tip light clusters of flowers 3 to 8 cm long held above the 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 very double and generally pure white or pale pink to purplish, centred on a pale yellow heart: they combine simplicity with floribundity.

Slightly scented 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 (-15°C to -25°C), it can be cultivated throughout many regions.

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

With its simple flowers, Arabis brings a country touch to naturalistic 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 caucasia ‘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 that covers whole plant. With its compact habit, it slips into any space to cover low walls, clamber up banks and carpet base of hedges.

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

See the product sheet

Arabis blepharophylla

Small deep-pink flowers cover a cushion of evergreen leaves. Moderately hardy, grown in regions with mild, relatively dry winters.

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

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Arabis ferdinandi coburgii Variegata

Forms a tapetum of glossy dark-green evergreen leaves marginate with cream, 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 flower colour. Forms a very effective matting groundcover, ideal for edging borders, in flowering paving or as a wall-top dressing.

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

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Arabis x suendermannii

A rather rare rockery plant, particularly decorative with its tiny evergreen leathery foliage, its spring, scented flowering which re-blooms easily in autumn. Perfect for emphasising a flight of steps, edge of a border or a gravel path.

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

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Arabis ferdinandi coburgii Old Gold

A silver-basket species with variegated foliage. Perfect as groundcover, for edging borders, in paving, on top of a low wall or on a stony bank.

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

See the product sheet

Planting

Where to plant Arabis or rock cress

Arabis is very resistant to cold and drought: most species are hardy to -20°C. It will therefore establish across France.

As quintessential rock garden plant, Arabis likes sun and well-draining soils.

Although it prefers fairly undemanding growing conditions — dry, stony and well-draining soil — it will adapt to richer, cooler, humus-bearing soil, though it tends to become more spreading and lose compactness. It will also tolerate sandy soils of seaside gardens very well.

It only dislikes overly compact soils and soils that stay 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 tendency to suppress weeds makes it an excellent alternative to lawn on dry sites. Groundcover by nature, it needs space and can tend to smother more delicate neighbouring plants.

The Silver Basket always brings a sense of lightness to compositions it inhabits.

While Arabis is the quintessential plant for naturalistic rock gardens (it is less suitable for highly formal rockeries), it will also make an excellent groundcover to casually carpet base of bushes or hedges, edge a border or path, run freely through paving, cascade over a dry wall or bank and flower in a pot or window box.

When to plant Arabis or Silver Basket

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

The Arabis or arabettes are perennials that benefit from being planted at density of 7 to 9 plants per m2, spaced about 30 cm apart to allow stems to spread 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
• Spread gravel in bottom of hole
• Plant without burying collar, covering it with 3 cm of soil
• Press soil lightly
• Water generously at planting

Planting Arabis or Silver Basket in a pot

Plant alone or in combination; even arabettes may invade or smother other plants. Choose a container wider than tall.

• Lay a good drainage layer (gravel or clay balls) in bottom of pot
• Plant in a mix of garden soil and leaf mould-based compost with equal part fine sand
• Water regularly

Arabis blepharophylla

Maintenance, pruning and care of Arabis

Rock cress is a truly undemanding perennial plant, tolerant of drought; it requires almost no watering. The first spring, give it regular waterings but avoid overwatering. Once well rooted, it will no longer require any water.

In a pot, soil dries out more quickly than in the ground, water generously during growth, allowing the substrate to dry out well between waterings. Water sparingly in winter.

Each year in autumn, apply a little compost if needed 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, after flowering, cut back clumps by half to maintain a compact habit.

Diseases and potential pests

Arabis is not very prone to diseases. White rust can affect foliage. Make sure to water without wetting foliage. Cut 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 pest, which causes galls that deform flowering stems; cut off and burn affected stems. Apply sprays of natural pyrethrum.

Arabis caucasica ‘Alabaster’

Multiplication

If sowing of 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

Division of clumps is the easiest way to multiply Arabis. It is carried out in autumn, after flowering.

• Using a fork and spade, lift clump and remove young rosettes with roots from clump’s periphery
• Plant them immediately and water until established

Associate

With its evergreen foliage and flowers in fresh tones, Arabis is indispensable in dry gardens, in mineral settings and in seaside, alpine or Mediterranean naturalistic holiday gardens where it forms superb, maintenance-free cushions all year round.

Arabis scopoliana in rockery (photo Michael Wolf)

Thanks to its delicate habit, it complements spring scenes with much charm, bringing 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 pairing 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, daffodils, tulips, scillas…

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

Combine with other rockery perennials such as small sedums, Iberis, moss phlox or aubrietas, or use as a matting groundcover for bulbous plants.

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