|A green-roofed house in Wales|
But green roofs now are different from back then. You can’t just lay down strips of sod on a building – most buildings aren’t built with a green roof in mind so don’t have the structural strength for it. Can you imagine how heavy a large scale lawn above your office would be after it rains? (or more applicable to Laramie, after it snows?)
Buildings that are constructed with a green roof in mind can plan ahead for it. Structural reinforcements are clutch. In fact, Switzerland mandates that all new buildings possess green roofs or walls - 25% of the surface area must be greened; Toronto has a similar law. And in Dearborn, MI, the Ford plant has a 10.4 acre green roof! That takes a lot of planning ahead!
Thanks to modern technology, green roofs are more feasible because of:
- Growing media. Modern green roofs use soilless “soil” that is lightweight and drains well. (More on the Berry Prairie soil soon.)
- Layers. Multiple layers create a green roof – the roof itself, a water-proof membrane, a drainage layer (involving a series of empty trays for collecting and draining excess water), a semi-permeable membrane to hold some water but drain extra, and the “soil.”
- Plants. Not every plant can rough it on a green roof. Many green roofs use only a select few plant species because they’re tough and stubborn. (This is where the Berry Center deviates from the norm.)
Not Just for Sedum
In the US, green roofs are commonly planted with sedum – a hard-core plant that can fight drought and extreme sun with the best of them. This species is good for people who want/need low-maintenance roofs, but it doesn’t do much for biodiversity. One species can’t attract many or an assortment of pollinators, spiders or birds, and it can’t create a mini-ecosystem.
An entirely different approach to green roofs is growing edibles (check out greenroofgrowers.blogspot.com). Creating a roof-top garden of tomatoes, peppers, squash and zucchini is a growing trend for individuals and schools, particularly in urban environments were open ground space is hard to come by. Low cost, few complications, high success and high versatility.
The Berry Center’s green roof is different yet. By planting almost 60 species of native plants, we hope to create a mini-ecosystem that teaches passersby about what thrives in the Laramie basin – including plants, bees, butterflies, beetles, arachnids and more.
Green Roof Gamble
But the Berry Prairie is experimental – one has never been planted at this elevation, and very few are planted in this style. Will this approach to green roofing work? Will the plants survive over the Wyoming winters? Is the growing medium right for these species? Will plants regenerate and reproduce to create a self-maintaining ecosystem? Will it require more water and nutrient inputs than we expect?
“The Grand Experiment” as Berry Center Director Greg Brown likes to call it. The questions are part of the fun.
|It takes a while for plants to established, but we're encouraged that many of them are flowering now.|
July 19, 2011
Written by Brenna Wanous, Berry Center