An Update on ASLA Green Roof Plant Growth
Richard Hindle gives a spring checkup in Washington, D.C.

Late last month, Richard Hindle, with Michael Van Valkenburgh Associates (MVVA), visited the ASLA green roof to research the condition of the roof’s plantings and to give an update report to national staff. Hindle, who holds a degree in botany from Cornell University and is currently studying landscape architecture at the Rhode Island School of Design, was pleased overall with the health of the roof. As the first and second plantings of last year have spread and matured, the roof ecosystem has become increasingly like a natural meadow. “The question now is, ‘How do you manage the health of a meadow?’” Hindle said.

Prickly cacti in bloom on the ASLA green roof; May, 2007.

"Horseweed" (Conyza canadensis), a noxious plant that needs to be removed from the roof.

A bright spot of growth on the south, experimental wave of the roof is the prickly cacti, which Hindle describes as “doing phenomenal.” The cacti are currently in bloom all across the south wave. He was also pleased to see that spurge growth has decreased on the roof. The sedum plantings placed under the grating on the green roof are also flourishing, furthering Hindle’s confidence in suggesting the use of aluminum grating as a feature of other green roofs. A problem weed now, however, is horseweed (Conyza canadensis), a noxious plant that needs to be removed from the roof. Hindle’s full report on the roof will be made available in the coming weeks. Visit the “Green Roof Central” page for more information about the green roof and links, including one to the live webcam.

A close-up on light yellow prickly cactus blooms; May, 2007.