Rock Cress

Aubrieta deltoidea, commonly called rock cress or aubretia, is a low, evergreen perennial that forms spreading mats of small gray-green leaves. Mauve, pink, or purple four-petalled flowers appear in spring and often continue into early summer. It is especially useful in rock gardens, gravel beds, wall crevices, and sunny slopes where drainage is sharp. ## Identification and placement The [RHS species profile](https://www.rhs.org.uk/plants/1909/aubrieta-deltoidea/details) describes a slowly spreading mat about 10 cm high and 10–50 cm across, with flowers from mid-spring to early summer. It lists full sun, tolerance of light shade, and well-drained chalk, loam, or sand with neutral to alkaline pH. The [RHS Aubrieta trial](https://www.rhs.org.uk/plants/trials-awards/ongoing-plant-trials/aubrieta-arabis-aurinia) notes that many garden cultivars derive from this naturally variable species. ## Establishment Set plants where water drains freely, especially through winter. Use a little more irrigation while new roots establish, then water during prolonged dry periods; the RHS trial added irrigation during an unusually hot, dry summer. Leave room for lateral spread. ## Maintenance After flowering, cut back lightly to maintain a compact mat. Inspect for aphids, flea beetles, or white blister, and remove affected material as needed. The RHS lists UK hardiness H6; that regional rating is not converted to USDA zones.