ArcheWild Native Green Roof Research Platform
ArcheWild enters its 3rd season (2016) of its native green roof research program in Philadelphia with outstanding results across all of its original design objectives, which include:
- 100% interesting and attractive East Coast native plants,
- Durable and self-repairing,
- Commercial engineering maximum of 4″ media depth,
- Virtually zero supplemental irrigation, and
- Ultra low-cost
100% interesting and attractive East Coast native green roof plants
Demand remains at an all-time high to create a pure native plant population on a green roof to provide a safe and functional haven for pollinators, butterflies, and other insects in an urban environment. Using plant species native only to the Piedmont and adjacent Ridge and Valley physiographic provinces is a primary motivator for this research platform so as to provide a regionally authentic experience for insects that do, or could, occur in the area.
As such, 100% of the plant species used for the research program were grown by ArcheWild from seed sources within a 150 mile radius of the test site, with most of plant species naturally occurring within a 15 mile radius.
There are no African sedum species. No midwestern prairie species. No alpine species. No non-native species.
A related design objective is to use species that are or could easily be made available in large volumes by high-quality propagation nurseries, such as ArcheWild Native Nurseries. With only a few exceptions (e.g., Manfreda virginica), the plant species chosen for the research platform could be contract-grown at the scale of 10,000’s of plugs per year.
Although few people actually get to closely interact with a green roof, it is important for the green roof to offer periods of both beauty and classic landscape architecture style. Peruse the image gallery above to see if this has been accomplished.
Durable and self-repairing
According to Dr. Rob Berghage, of Penn State University, the holy grail and ultimate achievement of any green roof program is the ability of the selected plant species to not only survive the wild climatic extremes to which they are subjected (durability) but for those plant species to actually set seed, germinate, and grow new plants (self-repairing). Most commercial green roofs find this objective quite difficult because the vast majority of species used are not heavy seed producers but instead rely on asexual reproduction for their long-term survival (e.g., sedums).
The ArcheWild Native Green Roof Research Platform has, so far, accomplished this coveted objective with several species demonstrating the ability to migrate from tray to tray to create an increasingly dense planting aesthetic.
Much of the science of getting seeds to germinate on a green roof is associated with media adjunct and layering technology that are proprietary to ArcheWild; our technologies are based largely on our plant propagation research studies at our Quakertown, PA facility.
Several media blends and layers are being tested in the current iteration of this research platform and some early-stage conclusions are being drawn. The next five years should solidify our understanding of media blends and layers that should allow ArcheWild to publish some initial recommendations.
Commercial engineering maximum of 4″ media depth
It is well-known that anyone can grow anything in 18″ of roof media, including tomatoes and palm trees. In fact, just 9″ of irrigated media is sufficient to grow most common native and non-native species. But commercial green roof installations and un-reinforced demonstration green roofs cannot support anything more than 4″ of media, which is the depth most commonly specified.
All trays used in the research platform have a maximum depth of 4″, suggesting that the planting design could be scaled to commercial installations.
Virtually zero supplemental irrigation
The green roof is outfitted with a zone irrigation system that allows for the testing of different media and irrigation combinations using components available at any full-service hardware store. The plantings were irrigated as allowed by LEEDS for early establishment after which the plantings were left largely to deal with the summer heat on their own. The research platform operator has the option of supplying periodic irrigation to prevent major losses during extended drought periods, but this has not yet been necessary. For the 2016 season, the operator is applying just 15 gallons of water per week, only as required, as a preventative maintenance practice across the entire 1000 square foot roof, which is a very low application rate.
Green roof contractors and material suppliers are making a fortune on very expensive and complicated membranes, trays, media blends, and automatic irrigation systems. The costs associated with ‘commercial’ systems make them prohibitively expensive to the point where no building owner would opt for a green roof unless required by their construction or retrofit permits. ArcheWild is proving that if you know your plants and their media (soil) and moisture requirements then anyone can construct a highly-functional, light-weight, and low-cost native green roof. The total cost per installed square foot for this research platform is significantly lower than any other tray system on the market and is highly competitive with the current lowest-cost method, which is 4″ of the most inexpensive roof media planted with Vinca minor.
Contact ArcheWild for consulting support on your upcoming green roof project: firstname.lastname@example.org.