Arabis

( AR - uh - biss )

At-A-Glance Information

Arabis, or Rockcress, is a genus that includes many flowering perennial and annual species which need full sun and moderate water to perform well in the landscape. Plants are low-growing and spreading, great for edges or borders, rock gardens and even as small-space groundcovers. Foliage is attractive year-round, and white, pink or rose-purple flowers bloom in clusters in springtime. Use these plants to fill in gaps in mixed beds and borders, to add interest to containers, or as a small-scale groundcover. The flowers will attract pollinators to the garden.

Arabis Species and Varietals

The genus Arabis is a member of the plant family Brassicaceae, and includes over 100 distinct species. The best growing zones for Arabis vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Arabis aculeolata (Waldo Rockcress)
This species of rockcress is native to a small area in the mountains of southern Oregon and northern California, and produces dark reddish-purple stems coated in white hairs. Leaves form a basal rosette, and are green and oval-shaped. Flowers are purple to pink in color. Individual plants reach up to 8-15 inches tall.

Arabis alpina (Alpine Rock Cress, Mountain Rock-Cress)
This species is native to mountain ranges in Europe, north and eastern Africa, central and east Asia, and parts of North America. Individual plants form a mat of green foliage and reach up to 16 inches tall when mature and in bloom. Loose heads of white flowers are present in springtime. This species is best in USDA hardiness zones 3-9.

Arabis blepharophylla (California Rockcress, Coast Rosecress, Rose Rock Cress)
This species grows best in USDA hardiness zones 3-9 or Sunset growing zones 5, 6, and 15-17, and is endemic to the rocky hillsides and ridges along the California Coast. Individual plants mature to about 8 inches wide, with fragrant rose-purple flowers held in dense clusters. Great in rock gardens and for adding color to container plantings. Variety 'Spring Charm' ('Fruhlingszauber') has magenta flowers that bloom in early springtime.

Arabis caucasica (Arabis albida) (Wall Rockcress, Garden Arabis, Mountain Rock Cress, Caucasian Rockcress)
This plant does best in USDA hardiness zones 3-9 or Sunset growing zones A1, 1-10 and 14-24. This is an original, dependable species that is native to Iran and the Mediterranean. Leaves are grey-green and form in a mat-like clump 6 inches tall and 1.5 feet wide. White flowers bloom profusely to form a fantastic, beautiful groundcover. Needs some afternoon shade in warmer climates. 'Variegata' has leaves with white margins, 'Pink Charm' and 'Rosabella' have pink flowers, and 'Flore Plena' is double-flowered.

Arabis ferdinandi-coburgi (Ferdinand's Rock Cress, Alpine Rock Cress, Variegated Alpine Rock Cress)
This species of Rockcress grows best in USDA hardiness zones 4-9 or Sunset growing zones 2b-10 and 14-24 and is native to Bulgaria. Plants form tight clumps to 4 inches tall and 1 foot wide, with white blossoms. Variety 'Old Gold' (pictured) has green leaves with margins lined in creamy yellow.

Arabis hirsuta (Hairy Rock Cress, Fringed Rock-Cress, Eschscholz's Hairy Rockcress, Creamflower Rock Cress)
This species is native to Europe, Asia, and the northern half of North America. It reaches up to 30 inches tall and produces white flowers that bloom between the months of June and August. Best in USDA zones 4-8.

Arabis lemmonii (Boechera lemmonii) (Lemmon's Rockcress)
This species of Rock Cress is native to western North America, from Alaska down through California and Colorado. It prefers to grow in rocky habitats. Individual plants reach up to 8 inches tall and produce pink to purple flowers. Foliage is light greyish-green. This species is not typically sold as a garden ornamental.

Arabis macdonaldiana (MacDonald's Rockcress)
This species is native to northern California and Oregon, where it prefers to grow in temperate coniferous forest openings. It is a rarely seen or cultivated plant, and reaches between 4 and 12 inches tall when mature and in bloom. Flowers are bright magenta.

Arabis procurrens (Spreading Rock Cress, Running Rockcress, Running-Eared Rock Cress)
This species does best in USDA hardiness zones 5-9 or Sunset growing zones 3-10 and 14-24 and is native to southeastern Europe. It has a creeping, wide-spreading habit with loose clusters of white flowers. The most common form of this species is 'Variegata', which has leaves heavily edged and splashed with white.

Arabis x sturii (Sturr's Rock Cress, Mountain Wall Cress)
This species of Rockcress forms dense clusters of bright green foliage that eventually spread to form low groundcovers. It grows best in USDA hardiness zones 5a-9b or Sunset growing zones 1-10 and 14-24. This species is considered to be one of the best rock garden plants.

Caring for Arabis

Plant your Rock Cress in an area of the landscape that receives full sun exposure. They need at least six hours of sun each day to bloom and grow well. If Arabis is grown in a spot that is too shady, stems tend to become leggy and flowers are not as profuse. These plants thrive in soils that are gravelly, rocky, or sandy and nutrient rich. They do well in soils that have a pH of between 6.2 and 7.2 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Lay down a thick (1-2 inch) layer of organic mulch around the planting area to suppress weed growth, maintain soil temperatures, and increase soil moisture retention. Ensure that mulch stays a few inches away from stems and foliage to discourage fungal issues. Water new plantings regularly as they establish a strong root system. At maturity, these plants are considered to be drought-tolerant, needing minimal waterings. In extended periods of drought, supply a little extra irrigation. They cannot tolerate waterlogged soil, which causes them to develop root rot issues. Make sure soil is allowed to dry out completely between waterings.

Fertilize yearly in early springtime with a application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Prune plants to trim back spent flowering stems and remove leggy growth. Avoid cutting into old wood, as this can inhibit new growth. Over time, these plants may develop a bit of a 'bald spot' in their center. This is a good indicator that the plant needs dividing, and typically happens every two to three years. For instructions on how to divide Arabis plants, see the Propagation section below.

Propagation

Arabis, or Rockcress, can be propagated either by using cuttings, by dividing existing plants, or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting or division method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Rockcress plant, follow the instructions below:

Propagating Arabis by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) peat moss and horticultural-grade sand or grit sand.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 3-4 inch portion(s) of the end of a non-blooming stem and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new flower.

Propagating Arabis by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) peat moss and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed pods are pretty easy to spot, they're left behind after flowers have faded at the tops of plants, and look like small, dried sticks. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes between 21 and 28 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Arabis by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost, and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in spring or fall (after the plant has entered dormancy and been cut to the ground, but before it has begun its new spring growth), and needs to be done every four to five years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:

Gather your materials. Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the roots. Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout.

Arabis seed pods form after flowers fade, and look like long, thin pea pods.

Arabis seeds are very small, and are typically brown.

Problems and Pests

Arabis plants have no serious insect or disease issues, though they can run into problems with the following if certain growing conditions aren't met: