A retaining wall with pockets for plants makes a great vertical landscape. This one, at the Elfin Forest home of Karen Gardner and John Phillips, combines pink and red ivy geraniums, yellow Bulbine frutescens, bougainvillea, and ice plants. The plants are rooted in a 30-foot-high cement grid that stabilizes an embankment at the base of a near-vertical slope. Amended soil fills wall openings; a drip system handles irrigation.
Several manufacturers make plantable (or "segmental") retaining walls, sold through building suppliers such as the Home Depot. Before installing any retaining wall higher than 3 feet or so, consult a structural engineer.
Ivy geraniums can be planted this month. Other colorful choices for walls: creeping rosemary (Rosmarinus officinalis) 'Huntington Carpet', dwarf periwinkle, rosea ice plant, and rose moss.
Behind the palms, ivy geraniums drape a cement grid that holds the slope, and the curtain of pretty red blooms extends to the driveway's edge.