In natural areas, invasive plants reduce habitat for native and endangered species, degrade riparian areas, overtake native grasslands and scenic areas and can interfere with recreational activities. Aquatic invasive plants threaten the ecological balance of the River. Take a look around the park and you will see examples of this invasion. J apanese knotweed surrounds an agricultural field just north of Tom's Creek, it can be found on many streambanks in large patches. Japanese stiltgrass invades wetlands.
Japanese barberry knows no boundaries and can survive in open space or forested areas.
Purple loosestrife is choking wetlands parkwide and threatening rare plant communities along the Delaware River. In the northeast U.S., it has virtually wiped out some native wetlands by establishing mono-specific stands. Eurasian water milfoil populations are increasing in the park as this invasive exotic moves upstream from the lower Delaware where it has formed almost a monoculture in the southern reaches of the River. One of the most aggressive exotics in DEWA is Ailanthus altissima , the Tree of Heaven. It spreads by seed, root suckers and stump sprouts.