Rooftop Landscaping

When to Start: Spring
At Its Best: Late spring to early autumn
Time to Complete: 1 day

Materials Needed:

• large lightweight containers
• gravel
• broken clay pot pieces
• multi-purpose potting mix
• slow-release granular fertilizer

• Calamagrostis x acutiflora
• bearded iris (not in flower)
• boxwood, Buxus sempervirens
• Panicum virgatum
• Stipa tenuissima

Site Your Containers

Select large zinc, galvanized or powder-coated metal containers that will not rust. Position rectangular pots close together to form a wall around your seating area, and use round ones to create focal points. Apply a thin coat of baby oil to zinc pots to clean off any marks and maintain their finish.

Add Planting

All plants here enjoy full sun and free-draining soil, conditions that suit containers on a roof terrace. Make sure pots have drainage holes, or drill some, and cover these with clay pieces. Then add potting mix, half-filling the containers. Apply fertilizer, and plant the grasses and boxwood. Add more soil to the iris containers and plant them so that the rhizomes (bulblike structures) lie on top of the soil.

Long-Term Care

Water in the plants well, and lay 2 inches of gravel on the floor. Water the containers regularly during spring and summer. The following spring, remove the top layer of potting mix and replace it with fresh potting mix, with some slow-release fertilizer. The Calamagrostis and Panicum are deciduous but their dried stems add interest in winter; the iris dies down completely, but reappears in spring.