First Advisor

Olyssa Starry

Date of Award

Spring 6-2025

Document Type

Thesis

Degree Name

Bachelor of Science (B.S.) in Environmental Science and University Honors

Department

Environmental Science and Management

Language

English

Subjects

Green roofs, Urban Sustainability, Companion planting, Ecoroof policy, Climate resilience

DOI

10.15760/honors.1714

Abstract

Green roofs, or ecoroofs, provide environmental and social benefits in urban areas. Ecoroofs manage stormwater by absorbing rainfall, reducing rooftop temperatures, supporting pollinators, and offering green space in densely developed cities. Portland, Oregon has adopted progressive policies that encourage green roof installation through incentives and building requirements. However, many ecoroofs in the city are underperforming due to poor maintenance, low public awareness, and limited access to rooftop spaces. This thesis explores whether companion planting can improve the ecological performance and long- term viability of extensive green roofs. A rooftop experiment at Portland State University tested the growth of radishes, with and without sedum, a drought-tolerant ground cover commonly used in green roofs. Two plots received the same soil conditions and no irrigation or weeding. Only the sedum-integrated plot produced harvestable radishes. The control plot with only edible plants produced flowers but no edible roots. These results suggest that sedum may reduce heat and water stress, supporting the growth of nearby plants. Companion planting could improve green roof performance under low maintenance conditions and enable additional functions like food production, education, and community use. Based on this study, policy recommendations include reinstating financial incentives, requiring routine maintenance, and encouraging accessible roof design. With stronger support, green roofs can better contribute to climate adaptation, ecological health, and urban equity.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/43821

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