Rock Cress 75 Seeds Compact Royal Mix Rock Gardens Hills Rockcress Beautiful Compact Royal Mix Rockcress 75 Seeds. Fresh for 2015 Planting. Great for Rock Gardens, Hills, Cracks in Walls, Steps, a Wonderful Addition. These guys like a sunny location to mostly sunny. Perennial. Very Hardy. In hot climates, they prefer partly sunny, Rockcress does well in fair or poor soil but needs good drainage! Germinate in 14 - 21 Days. (So be patient). Drought-tolerant once established. Grows to Height 2" - 4". Spreads up to 2' wide. Rock Cress is a compact, mat-forming, evergreen perennial with small leaves and iridescent flowers. Gently press into the soil after danger of frost in well-drained soil. Rockcress needs light to germinate. Keep moist at first but do not overwater.