The square footage of “green roofs” in North America’s cities grew 72 percent between 2004 and 2005 — and more than 80 percent in the United States alone, according to a new report from Green Roofs for Healthy Cities, a Toronto-based trade group comprised mostly of developers and building materials suppliers.

The report, released in April, says North America’s green roof infrastructure grew to about 2.5 million square feet in 2005, up from 1.3 million square feet in 2004. The top 10 cities ranked by square footage planted in 2005 were: Chicago; Washington, D.C.; Suitland, Md.; Ashburn, Va.; New York; Culpepper, Va.; Austin, Texas; Arlington, Va.; Des Moines, Iowa; and Ottawa.