Evaluating the effects of kelp (Ascophyllum nodosum), mushroom compost, and slow release fertilizer amendments on the growth, health, survival, and drought tolerance of plants growing on extensive green roofs

Abstract

Extensive green roofs offer the opportunity to grow plant species that are being lost due to urbanization. With shallow substrate that is low in organic matter and highly erodible, green roofs are a difficult environment for plants due to high irradiance, strong winds,and drought conditions. Kelp soil amendments can improve drought survival in plants but have not been tested on green roofs. Seed germination, early growth, health, and drought tolerance was evaluated using liquid kelp and slow release fertilizer (SRF) in a greenhouse experiment. Native plants and Sedum in green roof vegetated mats were also tested using kelp meal, mushroom compost, and SRF as amendments while measuring plant growth and erosion. Liquid kelp improved early germination, plant health and drought tolerance in the greenhouse experiment. The native plants thrived on the green roof and erosion on the vegetated mats was reduced with the application of the organic amendments.