5.2. ECCSR 05-18-2016 - Laserfiche WebLink

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clogging the drainage system. Since the roof at the Elk River plant is already slanted, we will not need the regular drainage system that flat roofs need. The next, and most variable part of the roof is the substrate mixture. The substrate, or soil, needs to be at least 3 inches deep and it has to be lightweight. The substrate we want to use for this green roof needs to be a mixture of native soil and an organic additive, such as wood chips or sand. This mixture will ensure that the plants will have enough nutrients to stay alive for a long time in both summer and winter. The last part of the green roof is the plant and vegetation, which we will talk about next in this report. _Plants Soil Draina Insulat` n Memo Structure Layers of Green Roof: http://www.lid-stormwater.net/greenroofs_specs.htm What kind of plants do we put on our green roof? Plants on a green roof struggle with the root space available to them and drought resistance. A small amount of substrate calls for a smaller root structure, and an irregular watering schedule means the plants should be fairly drought resistant. This narrows down the options for plants for the roof. Our Elk River partners expressed interest in using native flowering plants, which narrows the field further. Native plants are somewhat problematic for green roofs as Minnesota natives often react to drought by sending their roots further into the soil. These plants would obviously run into problems on a roof with a growing medium of approximately four inches. There are some native alternatives to sedum for green roofs in Minnesota. Recent research has shown that prairie plants native to Minnesota send their roots out horizontally as opposed to vertically when in a setting similar to a green roof.3 With this in mind we can explore some native flowering plants that would work for the specific green roof we are looking at in Elk River. 5