Arabis is a genus of herbaceous annuals and perennials and a member of the mustard family, Cruciferaceae, that also includes broccoli, radish, and stock. Although there are over 100 species in the northern hemisphere most are alpine species and only a few are suitable for the garden. Plants grow less than 12′ tall and form mats or tufts of often hairy downy gray evergreen leaves. The cruciform flowers are white to purple, fragrant and appear in loose racemes in spring. The genus name, Arabis, may come from Arabia where some members of the genus are native.Rock cress’ like cool climates, full sun, and lean to average well-drained limey soil. They tend to melt out in the center in hot weather and can profit from afternoon shade in the South. Shearing plants after flowering helps maintain an attractive appearance throughout the summer. Propagation is by seed, division or cuttings in spring. Division after flowering every 2-4 years keeps them vigorous. The small size of the plants recommends them for front of the border and rock gardens and they are especially attractive with spring bulbs.
Recommended Arabis species:
A. arendsii
A cross between A. caucasica and A. aubrietioides, this hybrid forms procumbent cushions of rosettes with hairy, gray green leaves, similar to A. caucasica. It has pink flowers, however, instead of white. Cultivars include ‘Rosabella ‘(compact, light green foliage, rose pink flowers) and ‘Spring Charm’ (bushy, large carmine flowers)
Height: 6-9″
Flower Color: Pink
Hardiness: Zones 4-9
California Rock Cress aka Rose Cress (A. blepharophylla)
Endemic to the San Francisco Bay area and nearby areas, this species forms flat rosettes of dark green basal leaves 2-3″ long and unbranched stems bearing large clusters of purplish pink flowers.
Height: 6-12″
Flower Color: Purplish pink
Hardiness: Zones 6-9
Wall Rock Cress (A. caucasica aka A. alpina, aka A. albida)
Procumbent cushions of gray green rosettes with leaves 1-2″ long give rise to elongated racemes of 1/2-1″ flowers. Cultivars include ‘Flore Plene (double flowered), ‘Variegata’ (leaves green and cream), ‘Snow Peak’ (compact, 4′ tall)
Height: 6-9″
Flower Color: White
Hardiness: Zones 4-10
A. ferdinandi-coubergi Variegata’
Compact plants with waxy leaves with white margins make this arabis eye-catching. ‘Old Gold’ has yellow variegated leaves.
Height: 2-4″
Flower Color: White
Hardiness: Zones 3-9
A. procurrens
Low mats of glossy bright green foliage spread vigorously by rhizomes.
Height: 6-12″
Flower Color: White
Hardiness: Zones 3-9