Rock cress

Sun

Full sun; light afternoon shade is helpful in warmer gardens.

Water

Water regularly while establishing, then during prolonged dry spells. Let the soil surface dry between waterings; avoid persistently wet roots.

Soil

Well-drained, gritty or sandy soil, preferably neutral to alkaline. Tolerates poor soil but struggles in wet clay.

Height

0.5-1 ft (0.15-0.3 m)

Spread

1-1.5 ft (0.3-0.45 m)

Flowers

Early to late spring, depending on climate; usually white, with pink-flowered cultivars also available.

Foliage

Evergreen. Small, softly hairy, grey-green leaves form low mats.

Growth

Moderate

Care needed

Low

• Pollinators
• Drought tolerant
• Cold hardy
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.7 ft (0.22 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US and Canada

Growth rate

Moderate

• Plant with the crown at soil level in a freely draining position.
• Water new plants during dry weather until their roots are established.
• Avoid rich feeding; use a light spring feed only if growth is weak on very poor soil.
• Use a thin gravel mulch around the crown rather than moisture-holding organic mulch.
• Renew sparse, woody mats with cuttings or rooted outer shoots.

Pruning. Immediately after flowering, lightly shear off spent flower stems and trim straggling shoots to keep the mat compact. Avoid cutting deeply into old, bare stems.

Early spring

Remove dead foliage and check that winter moisture has not left the crown sitting in wet soil.

Spring

Plant in well-drained soil and water during establishment.

Late spring

Trim after flowering, adjusting the timing to your local flowering season.

Summer

Take non-flowering shoot cuttings and water established plants only during extended dry spells.

Early autumn

Plant rooted cuttings in mild climates, allowing time for roots to establish before winter.

Winter

Keep fallen leaves and wet debris off the mats, and check drainage around plants in containers.

• Let it trail over a low stone retaining wall for a spring cascade of flowers.
• Plant between rocks in an alpine garden, keeping the crown clear of standing water.
• Use along a sunny border edge with dwarf spring bulbs for overlapping seasonal interest.
• Combine with aubrieta and creeping phlox in a raised gravel bed for contrasting spring flower colours.

Garden styles it suits: Alpine rock garden, Dry gravel garden, Cottage garden, Cotswold cottage, White garden and Low-maintenance.

Plant it with: Aubrieta, Creeping phlox, Candytuft, Dwarf irises, Species tulips and Creeping thyme.

Wildlife: The spring flowers provide nectar and pollen for bees and other early-season insects.

• Root or crown rot in wet soil: improve drainage, keep mulch away from the crown and replace badly affected plants.
• Aphids on young shoots: rinse off small colonies with water; use insecticidal soap if needed, avoiding open flowers.
• Sparse, woody centres: trim lightly after flowering and replace ageing plants with rooted cuttings.
• Summer decline in hot, humid weather: provide good air circulation and light afternoon shade, and avoid overwatering.

Not known to be toxic to people, cats, dogs or horses. No particular plant part is recognized as poisonous, but it is an ornamental rather than a food plant.

• Aubrieta (Aubrieta deltoidea)

  Usually has purple or violet flowers and smaller leaves; rock cress usually has white flowers and more conspicuously grey, hairy foliage. White-flowered aubrieta cultivars can be harder to distinguish.

• Evergreen candytuft (Iberis sempervirens)

  Has narrow, smooth, dark-green leaves and flat flower clusters whose outer petals are noticeably larger; rock cress has hairy leaves and flowers with four more evenly sized petals.

• Rose rock cress (Arabis blepharophylla)

  Usually has deep pink to purple flowers and greener leaves fringed with prominent hairs, rather than the generally white flowers and grey-green foliage of Caucasian rock cress.

The epithet caucasica refers to the Caucasus region, while the common name rock cress reflects its rocky habitats and cress-like flowers.

Propagation. Take short, non-flowering shoot cuttings in early summer, or detach rooted shoots from the edge of a mat in spring. Seed can be sown in spring, but named cultivars may not come true from seed.

Accepted botanical name

Arabis caucasica Arabis alpina subsp. caucasica is an older name for Arabis caucasica.

In the US and Canada

Native in Canada, Greenland and the lower 48 states.

Native range

Albania, Algeria, Bulgaria, East Aegean Is., Greece, Iran, Iraq, Italy, Kriti, Krym, Lebanon-Syria and Morocco.

Measured

Soil pH 7.5 to 8. Average height 4 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.