As many professionals know, vegetated roofs are designed and sold for a variety of reasons to solve easy and complex problems. Often, the maintenance falls into a standard form that is handed to an owner within the closing documents of the entire construction documents. However, manufacturers and growers who set these simple standards are often not involved after the installation has been completed, and never return back to the roof site. Owners are left maintaining the vegetated roofs (which is very different from at grade landscape management) whether or not they have experience in roofing or landscape.
As is common with any new technology, facility managers may question an irrigation schedule, the necessity to weed, and what to do if certain areas of the roof under-perform. The best thing we as designers, installers, and manufacturers, can do in advance of closing documents is to create the most resilient ecosystem by designing a defensive plant palette that fits within the microclimate of the rooftop, and stay in regular communication with the owner and/or facility manager by filling out reports, just like GREENFORMATIONTM.
I recently converted a green roof owner after the installer requirements were completed to hiring a maintenance consultant, my company AD Greenroof. In Minneapolis this year, we experienced a prolonged winter. (I’m not going to discuss the 18” snow storm we got on May 2, that was ridiculous!) Plants were slow to emerge and green up. Aside from a few industry professionals, no one was thinking about maintenance. Of course, after a few warm sunny days, the plants really started coming around, and so did their competitors. By the second week of June, I saw common green roof weeds encroaching on the roof. However, after all the approvals and scheduling the crew to work, some of the weeds had already set flower and seed. While keeping within the budget, we found creative solutions to managing the weeds.
Designing a resilient green roof includes “early and often” maintenance. In addition to weeding, thinning also happens. Thinning occurs when intended plants get aggressive and may crowd out other species. It’s important to keep diversity and healthy intended plants! I haven’t thinned many Sedum based roofs, but I certainly have with native and other herbaceous forbs.
Ah, bring up the bags, it’s time to pull some plant biomass!