Invasive Plants

In North America many invasive plant species were introduced purposely as either ornamental garden plants, or for use as land stabilizers (i.e. along steep slopes, riverbanks, or floodplains). Others were accidentally introduced with seeds of agricultural or horticultural crops. Invasive plant species are incredibly threatening to natural communities because they spread very quickly, alter the natural balance of habitats to change plant and animal communities, lead to a decrease in plant diversity, and deplete natural resources. It is often very difficult to eradicate invasive species.

The spread of invasives is an immense threat throughout the world. In the United States, invasive species are the top threat to the preservation of natural ecosystems in the National Park System. In the Chicago Region, about 11% of the approximately 1350 non-native plant species are considered invasive. The description pages for all taxa we consider invasive are marked at the top, as well as in the regional occurrence section.

purple flowered plant in wetland

Purple loosestrife, Lythrum salicaria, is an incredibly harmful invasive plant that was introduced to North America from Eurasia and has spread into wetlands across the continent.

Information provided on this page applies to the Chicago Region and may not be relevant or complete for other regions.