Common aubrieta (Aubrieta deltoidea) creates a grey-green ground cover punctuated with abundant purple flowers in late spring and summer. The creeping perennial, ideal for borders and pathways, can even thrive tucked into nooks and crannies in a rock wall. Common aubrieta, also found under the common name false rockcress, grows in U.S. Department of Agriculture plant hardiness zones 4 through 9.
Selecting Sun, Sandy Soil and Rocky Terrain
Common aubrieta grows well in sandy soil with good drainage or in a rock garden. It doesn't require much soil, making it a suitable choice for crevices in rock gardens and rock walls. Grow this ground cover in full sun - more than six hours per day - for optimum growth and vigor. If the garden is partly shaded - between two and four hours per day - you can still grow this trusty ground cover though it may grow less vigorously.
Spacing Ground Covers and Rockeries
Create a even ground cover with a 12-inch spacing between plants, staggered rather than in formal rows for a natural look. When checking the distance between each plant, measure from the base of each stem. If you're growing common aubrieta in a rock wall, spacing depends on how much stone you want to see. Each plant grows 2 feet wide, so if you want the plants as an accent while leaving some stone exposed, leave 3 to 4 feet between plants or more, depending on the final coverage you want.
Watering in Inches and Gallons
Common aubrieta needs water once a week. Use a sprinkler or a soaker hose to water the area thoroughly until it's damp down 4 to 6 inches. During rainy weather use a rain gauge to help calculate how much natural precipitation is contributing to the watering schedule. Common aubrieta grows well with 1 inch or water per week. When watering a rock wall or rock garden, make sure the water is penetrating the soil inside the rock crevasse where the roots are growing, but water gently so as not to dislodge the soil. Use 1/2 to 3/4 of a gallon once a week for each plant.
Applying Fertilizer Annually
Fertilize once either in the fall or early spring. Apply a 16-8-8 granular fertilizer and sprinkle evenly over the soil under the foliage. One-half cup covers a 25-square-foot area. After fertilizing the area, give common aubrieta a thorough watering, soaking the soil 5 to 6 inches deep. Rinse off stray fertilizer that got on the leaves at the same time.
Weeding and Mulch Use
Once common aubrieta gets established, the dense mat-forming growth habit helps keep the soil moisture from evaporating rapidly and keeps the weeds down. During the first few growing seasons, use a layer of mulch - like sawdust, leaf mold, pine needles or another organic material - to protect the soil and minimize weeds. Spread it 3 inches deep over the area after planting. Although established ground covers like common aubrieta keep weeds down, a few are likely to sneak through. Pull any you find by hand so you don't accidentally damage the roots.