Finding Flora Fit for the Front Range (and Further)

Gardening on the Front Range comes with unique challenges: low precipitation and humidity, high solar radiation, relatively short growing season, alkaline clay soils, and extreme and unpredictable weather changes and patterns. Many common plants in the horticulture trade can’t thrive in these conditions without being coddled, so it can be a challenge to find plants that flourish in our region. The Plant Select® program and Denver Botanic Gardens seek to do just that. At our trial garden at Chatfield Farms, we trial plants to see how they perform for this region, before they’re introduced to consumers.

Potential plant introductions with landscaping potential are chosen by Gardens staff and Plant Select partners; plants are often selected for having a pleasing growth habit, unique flowering color or other desirable aesthetic traits. 

Once a plant is chosen, 10 individuals are planted in evenly spaced rows. Over the course of three years for herbaceous plants and five years for woody plants, assessments are taken for growth, flowering times and intensity, pest and disease tolerance, seedling/rhizome recruitment and spread, and overall aesthetics. Additionally, the amount of water applied is recorded and methods for best propagation are explored for each plant being trialed. Pollinator observations are also performed to discover if the plant may be good habitat for pollinators and which pollinators a plant attracts. Lastly, photos of the plants are taken across the season, creating a time series of how the plant appears throughout the year.

The goal of these evaluations is to find plants that perform well with low water inputs and can handle the cold winters and hot, dry summers. If we are looking at plants that flower, they should be ones that flower prolifically and in an aesthetically pleasing way; if the plant is supposed to be evergreen, it needs to suffer little leaf death in the winter. 

A plant may not make the cut if it looks great early in the growing season but suffers from a disease or pests heavily later in the season. If a plant is not native to the region, understanding if the plant aggressively reseeds or spreads rhizomatously is important so that a plant is not introduced that could potentially become invasive.

While this work has largely been focused on the Front Range region of Colorado, a sister trialing site has been initiated this year in Kaysville, Utah at the Utah State University Botanic Center. This allows the plants to be tested in different conditions, especially climate and soil. For example, a plant that may not be hardy in our trial garden at Chatfield Farms, may be hardy in Kaysville, which is a USDA hardiness zone warmer than Denver. This allows the program to better evaluate plants for the overall mountain west region, not just the Front Range. By expanding trial locations and improving the breadth and rigor of data collected on plants in trial, we hope to increase the diversity of plants accessible to consumers that are a better fit for the climate of this region.