Dictionary of Flowers: Aubrieta (Rock Cress)

Lovely delicate Aubrieta (Rock Cress) in close-up. Image used under a Creative Commons licence with the kind permission of Tom Bech and Flickr

Aubrieta
Common name: rock cress
Family: Brassicaceae
Category: Perennial in USDA zones 4-7
Height: 6" to 12"
Width: 18" to 24"
Sun
Blooms: late spring to early summer
Growth habit: mat form. Used as a filler or spiller in container combinations
Maintenance: easy
Soil: average to poor, alkaline, free draining. Water regularly if grown in containers. Drought tolerant when established
Garden uses: containers, front of mixed border, rockery, ground cover
Diseases: downy mildew
Pests: pest free

Aubrieta is a short herbaceous perennial that forms a mat like cover over the ground, trailing from the edge of rock gardens or containers. It is also used as ground cover. The plant spreads by rhizomes.

The small flowers can be pink, purple pink or red. They cover the plant during late spring and early summer for three to four weeks, forming a carpet of color over areas of the garden.

It prefers full sun, but can be grown in part shade in average to poor, alkaline soil.

Plants grow better if nights are cool and humidity is low.

Fertilize rock cress in spring, before it starts blooming and during summer with a balanced slow release fertilizer.

When done blooming, cut aubrieta down by half to encourage another possible bloom cycle.

Seed can be collected after the second bloom cycle, or the plant can be deadheaded to prevent self-seeding and to keep it tidy.

Rock Cress fills gaps beautifully. Image used under a Creative Commons licence with the kind permission of Distant Hill Gardens and Flickr

Rock cress can be grown from seed. Plant seeds indoors during late winter in moist seed starting mix, making sure the mix drains well. Barely cover seed. Seal in plastic bag. At 65F, aubrieta seed sprouts in 14-21 days.

When seedlings are large enough to handle, transplant to larger containers. Plant 12" apart in desired spot after danger of frost has passed.

Aubrieta can also be propagated by division of clumps and by cuttings.

White Rock Cress. Image used under a Creative Commons licence with the kind permission of nociveglia and Flickr

Aubrieta is deer resistant. Pests seldom bother it. If grown in too wet conditions, it can develop downy mildew. Treat with an antifungal and cut down on watering or improve drainage.

Popular varieties:

Aubrieta deltoidea 'Elsa Lancaster' - a dwarf variety with deep purple flowers
Aubrieta deltoidea 'Red Cascade' - deep rose-red flowers, short, spreading
Aubrieta deltoidea 'Blue Beauty’ - blue-violet flowers with somewhat ruffled petal edges
Aubrieta deltoidea 'Argenteovariegata' - variegated foliage, very short variety (two to four inches) with blue-purple flowers
Aubrieta hybrids 'Axcent' series - available in several colors, it blooms earlier and longer than other aubrietas

A view of a cluster of Aubrieta flowers. Image used under a Creative Commons licence with the kind permission of Elizabeth McClay and Flickr