By Andrew Yanders
Last Friday I drove up to Newtown Square, PA to check-up on two green roofs we installed earlier this summer at the Episcopal Academy. I was joined by two of our Philly friends from Urban Ecoforms, Zach and Jared.
July was a remarkable month. The extreme heat coupled with the lack of precipitation made the first days of establishment especially stressful. We placed the roofs on a strict regime of water - beginning with the first week and gradually reducing the amount of water week by week until irrigation ceased after 4 weeks.
As expected, many of the plants did exceptionally well. Notably, Delosperma cooperi and Allium schoenoprasum had no problem handling the conditions. Our Sedum cuttings did not fare so well. The surface of the growing media dried too quickly and became too hot for roots to adequately form.
This hot area on the roof where the cuttings did not establish well was planted with a couple of trays of Sedum sexangulare and Sedum reflexum and a five gallon buckets worth of assorted Sedum cuttings was again spread. The weather has cooled significantly in August and we feel the Sedum cuttings should establish nicely this time.
Planting a green roof is not a precise science. Trial and error is the only way to find out if a species is going to work or not in a specific location. We are finding out on the Academy roof that shading is creating two distinct zones on the small 700 sf roof. The temperature and exposure difference between the two zones is dramatically impacting the growing habits of the plants on the roof.