I’ve been meaning for the last month to get some posts up for Ecoroof month, and it just hasn’t happened… So now that the events are over, and a bike tour has been through our house, I have an update. Recently we did a little maintenance work on our entry ecoroof with a few additional plantings. Last summer was not entirely kind to the ecoroof over our entry, specifically it was not kind to the strawberries planted on it. We had a couple of weeks where we saw temperatures over 100° that dried out the roof so much that the strawberries were unable to recover. Other plants have done quite well, the camas has been shooting up over the last month, and nodding onions not only survived the heat but have reseeded like crazy with hundreds of new sprouts growing in.
One of the patterns we’ve been noticing with our roofs over the course of the last year is that the plants that have done the best are the ones with a strong seasonal response. We have had 100% survival with our licorice ferns, which go dormant in July only to spring back in October once the rainy season starts to set in. Camas is dormant in all but the spring, and nodding onions, while green all year, send up flowers once the weather turns hot and dry. We had been discussing this for a little while and then we attended a talk hosted by the city of Portland by Stephan Brenneisen who was advocating this approach as one of many strategies for improving urban habitat and biodiversity and encouraged everyone to consider that an ecoroof that dries out in the summer only to spring back with the rain is actually quite healthy and appropriate for our environment.
We are currently in the process of revising/amending our plantings a bit to reflect our new thoughts about how we would like our roofs to operate. This last week we went through and planted meadowfoam, which will die back but reseeds readily (and is responsible for tasty honey) as well as some Sedum spathulifolium... Although we are planning on minimizing our roof’s reliance on sedums, we feel like a little bit of native sedum is appropriate for variety. Soon we plan on adding some ferns to our entry ecoroof, and we will be working on seed mixes that we plan on broadcasting in the fall on all our ecoroofs to improve plant density and diversity.