Naughty or Nice? Monitoring the Gardens’ Watch List Species

It can be easy to think of a garden as separate from its surrounding environment. After all, the plants in a garden are predominately selected, grown and managed by human hands, a far cry from the myriad ecological factors that shape wild plant communities. Despite this difference, the boundary between a garden and its surroundings is far from impermeable. Under the right conditions, introduced garden plants can escape and start growing in nearby areas where they don't naturally occur. Though infrequent, these garden escapees can become invasive, potentially harming the local environment, economy or human health.

To reduce the risk of unintentionally introducing invasive plant species through the ornamental plant trade, Denver Botanic Gardens monitors a list of ornamental plants with traits similar to those of known invasive species. As the Watch List Species Intern, I helped collect data on these “watch list” plants to help determine the invasive potential of these species. Data collection consisted of several components. Watch list plants were mapped throughout the Gardens (with a great deal of assistance from horticulturists) to assess their spread and the effectiveness of control measures. This information was then entered into the Gardens’ database for its living collection so that it can be referenced at any time in the future.

Next, watch list plants were collected to be preserved as herbarium specimens. These specimens can then be used to confirm the identification of watch list plants as well as document where that species is located at the time of collection. The final portion of my internship was conducting weed risk assessments for several watch list plants. A weed risk assessment consists of 40 yes-or-no questions about the plant’s life history, climate tolerance and known ecological or economic impacts. A score is generated based on the answers to the questions, which can then be used to estimate the invasive potential of a plant.

Contributing to the watch list project as an intern at the Gardens was both a rewarding and revelatory experience. The amount of work done behind the scenes to ensure that plants in the Gardens’ living collections are responsibly selected and managed is truly awe inspiring. Moreover, learning from experts in horticulture and ecology at the Gardens was an incredible opportunity, and it was a privilege to do so while helping to address an important issue facing the horticulture industry.

This article was contributed by Seth Polich. He recently graduated with a master's degree in biology from West Chester University of Pennsylvania, where he also cared for the university's teaching greenhouse. Originally from the Colorado Springs area, he is happy to be back exploring the diverse flora of his home state.