Nonnative Species

One of the largest threats to the park’s flora is the ever-growing population of exotic (non-native) invasive species. The prevalence of invasive plant species has been a concern for several decades. Invasive species exhibit rapid and prolific growth and therefore out-compete native vegetation for space, light, water, and nutrients. As a result, they tend to displace native vegetation. The absence of native vegetation results in degraded habitats for native animals. Exotic invasives can alter entire ecosystems and threaten biodiversity, if kept unchecked.

Thirty-five percent of the plants identified in a 1985 flora and fauna study were found to be exotics (Cypher et al. 1985). As of early 2001, 20 miles of forest edge and 900 acres of woodlands were infested with invasive vines and shrubs. The most problematic invasive species in the park are

• Mile-a-minute
• Canadathistle
• Japanese knotweed
• Japanese barberry
• Japanese hops
• Crownvetch
• Miscanthus
• Oriental bittersweet

At Valley Forge NHP, exotic invasive species colonize the bare ground left by severe heavy browsing by white-tailed deer. White-tailed deer evolved to eat native plants, and rarely browse the exotics that plague the forest. This selective browsing has exacerbated the spread of the exotics.

 

Learn more about the invasive Spotted Lanternfly!