The Case for Perennial Gardens in Water Conservation
Rudbeckia fulgida ‘Goldsturm’ and Agastache Cana intermingle bring vivid color to a water-wise garden.
By Emily Morris
September 25, 2020
During one of the worst wildfire seasons on record, caused in large part by unprecedented heat and drought, water conservation is top of mind at Tree of Life; and one way we always partake is through the design and installation of perennial gardens. Let’s delve more into why water conservation matters and how perennial landscapes can contribute to the effort.
Why Water Conservation is Important
In statistics laid out by the US Bureau of Reclamation, we gather that about .5% of the Earth’s water supply is available for human use (the rest is ocean water, locked up in ice caps, or too deep to extract). Now and in the future, we face a deficit between the amount of water we use and the rate it can be naturally replenished and distributed.
According to a National Geographic article entitled, “Why is America Running Out of Water?” shortages could occur in 83 out of 204 basins as early as next year, and while temperatures continue to rise, drier areas will see more droughts, while wet regions will see more storms of intense, difficult-to-capture rainfall. In the Rocky Mountains, snowmelt will begin and end earlier, leading to shortages later in the summer. Methods to unlock more water, like desalination (removing salt and minerals from ocean water) or piping it in from far regions incur high amounts of pollution and cost. The simplest answer to meeting demand lies in conservation.
How Good Landscape Design Contributes to Water Conservation
To see how water conservation can be successful, let’s look at a case study: the city of Los Angeles where urban water use has fallen since the 1970’s, despite a population boom of 10 million. To achieve this success, the state legislature used pricing incentives for water conservation, mandated conservation technologies like low-flow toilets and showerheads, and restricted the use of water on landscape. From 1990 to 2010, water use fell by 22%, and from 2010 to 2015, it fell another 19%— largely due to the reduction of landscape watering.
In Colorado, a large part of municipal water use goes towards commercial and residential landscapes, and within that, mainly sod. As an alternative, perennial gardens can be designed to need just a small supplement to natural rainfall, acting as a beautiful, immersive tool for water conservation. In drip irrigation vs. sprinkler systems, efficiency lies at 95% vs. 40-80%, meaning virtually no water is lost to evaporation in drip irrigation. One five-year study of xeriscape conversions at single-family homes showed a water conservation rate of 18-63% compared to sod landscapes. A larger movement away from sod and towards xeriscapes could contribute greatly to Colorado’s water conservation efforts.
Salvia and Allium bring beauty to a commercial landscape in Denver, CO.
How Tree of Life Designs for Water Conservation
First and foremost, Tree of Life’s landscape designs aim to connect users to the local environment and a deeper sense of nature in their urban/suburban settings. In letting the rhythms of nature guide us, we naturally design to complement existing natural patterns, resulting in largely self-sustaining, low maintenance, and long-lived gardens. Our plant palette exclusively includes plants well-adapted to the Front Range, most having a very low water demand, and they’re combined in such a way that plants can commingle in communities that mimic the way plants grow in nature. You can begin to explore water-conserving landscape plants within this sampling of native, low-water options in the Tree of Life plant palette:
Rhus trilobata ‘Autumn Amber’
Achillea ‘Moonshine’
Asclepias tuberosa
Solidago ‘Golden Baby’
Penstemon pinifolius
Amorpha canescens
Bouteloua gracilis
Schizachyrium scoparium
Amelanchier alnifolia