Toward low-maintenance extensive green roofs: A review for plant selection and substrate design

Abstract

Extensive green roofs (EGRs) are gaining popularity worldwide due to their environmental and economic benefits. A primary goal of EGRs is to achieve low maintenance to reduce costs; however, this is often challenged by harsh environmental stresses and limited substrate depth. These challenges can be mitigated through strategic plant selection and substrate design. Despite substantial research on plants and substrates under natural or controlled low-maintenance conditions, a consensus on optimal strategies low-maintenance EGRs (LEGRs) remains elusive. This study reviews 87 articles related to LEGRs, focusing on plant selection and substrate design. Plant selection is evaluated based on three criteria: ecophysiological characteristics, origin status, and establishment. Plant life form, such as forbs, grasses, and succulents, prove effective, with sedums remaining highly suitable for LEGRs. Native plants are gaining attention, while spontaneous plants may provide long-term advantages. Substrates composed of traditional lightweight materials with low organic content support plant performance on LEGRs, with a substrate depth of 10–15 cm being sufficient for sustainable LEGRs. Over 40 % of LEGRs require no maintenance, while low maintenance primarily focuses on irrigation. These findings suggest that LEGRs can succeed in most temperate regions. By integrating plant selection, substrate design, and maintenance strategies, we propose a conceptual framework to facilitate the success of LEGRs. This review offers a valuable reference for implementing LEGRs and the proposed framework can benefit LEGR designers, owners, and stakeholders.