Japanese Knotweed was brought from eastern Asia as a garden plant. This perennial herb grows up to 10 feet tall, with heart-shaped leaves and white flowers. It invades a wide variety of habitats and forms dense thickets of bamboo like vegetation that aggressively outcompete native plants, and negatively impacts wetland and riparian (water’s edge) areas.

A deciduous tree, black locust was brought here from the Appalachian and Ozark Mountains for erosion control and durable wood. It has white flowers, compound leaves, and thorns. It can grow up to 100 feet high. It invades fields, grasslands, and open woodlands. It can increase soil nitrogen levels, which threatens native plants that are adapted to nitrogen-poor soils.

Goutweed is a perennial herb from Asia that was likely introduced as a groundcover for landscaping. It’s usually under 1 foot tall, but its flower heads, with their small, white blooms, may reach 3 feet tall. It often invades woodlands next to areas where it has been planted, and can spread from discarded yard waste. Its dense growth crowds out native plants.