With the new green roof ordinance in Denver, you might be seeing a lot more green towards the sky in the mile high city. But what sort of plants can survive the windy arid environments of a rooftop in a state like Colorado?
Sedum plants (more commonly known as stonecrops) are leaf succulents with up to 470 different species. Their flowers (which often have five petals) add a nice decorative element to green roofs that are installed for functionality and cost savings. Because their leaves retain water they are preferable to grass on green roofs, especially for modular systems (4). The EPA Building in Denver has an extensive modular green roof with a primarily sedum cover. Some of the variety of sedum plants used are Sedum acre, Sedum album, Sedum kamtchaticum, Sedum spurium ‘Dragon’s Blood’, Sedum spurium ‘John Creech’, and Sedum spurium ‘Red Carpet’ (3).
Other succulents, such as aloe vera, are also great plants to have on a green roof, especially one that is accessible. Many succulent plants have a unique and ornamental appearance, so they are perfect for green spaces while also perfect for the arid climate of Colorado. A study conducted by Colorado State University found that the succulent species overall as a group (compared to other species tested) maintained a healthy state five time longer than the next best species tested (herbaceous). Their revival rate was double that of others (1).
Beyond water retaining plants such as succulents and cacti, prairie grass such as Blue grama is also a popular choice for green roofs in Denver. The flagship REI store green roof features this particular grass, as well as a combination of shrubs and perennials (2). It also happens to be the official state grass of Colorado, and is often found in our beloved Rocky Mountains.
Last but certainly not least is our favorite plant selection for green roofs: food. Despite what you might assume, green roofs are great environments for planting vegetables, herbs, and various other edible goodies. Because of their highly contained environment, away from the garden variety of pests and plant diseases, they give plants an opportunity to thrive much like a container garden. Don’t believe us? Just ask The Gathering Place, Denver’s own daytime drop-in center for women and children experiencing homelessness. Their roof features a safe playground and garden that supplies some of the food used in the kitchen. The kids are often involved in the caretaking of the plants, making it educational and fun to boot (2).
Now that you know what sort of plants you can grow in Colorado, maybe you’re thinking a getting a green roof yourself!
Extensive green roofs in Colorado: Plant... (PDF Download Available). Available from: https://www.researchgate.net/publication/277323508_Extensive_green_roofs_in_Colorado_Plant_species_performance_growing_media_modifications_and_species_response_to_growing_media_dry_down [accessed Jun 07 2018].