A group of Seattle condominium owners didn't horse around when they decided to share a rooftop garden. With no ground to cultivate, Linda and Greg Harris, Greg Kucera, and Larry Yocom came up with an ingenious solution: an all-container garden using livestock watering troughs.

Purchased from a local feed store, the galvanized steel troughs come in oblong and round configurations with 2-foot-tall sides and diameters up to 10 feet across. The condo owners consulted with a structural engineer before placing the troughs on the roof. They drilled 2-inch drain holes in the bottom of each one (about one hole per 2 square feet). They spread 5 inches of gravel over the bottom and topped it with commercial potting mix.

Next, with help from garden designer Pam Roy, they chose an assortment of plants for each trough. For upright accents with delicate scale, they planted Chinese witch hazel, Japanese maples, and mugho pine. Texture and seasonal color come from annuals, callas, crocosmia, and irises. In some troughs, cotoneasters spill over the edges to the gravel-covered roof.