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!
