Terrestrial Invasive Plants
Giant hogweed, a noxious, invasive plant, was confirmed for the first time in Hamilton County in the summer of 2013. This plant can threaten public health and safety and the environment.
Purple loosestrife is established throughout Hamilton County, especially along transportation corridors, gardens, and riparian areas . It spreads by seeds and rhizomes. Showy, magenta flowers bloom in the summer. Stems are square and leaves are lance-shaped. Manage by pulling or digging small plants. For large plants, first clip flowers, then cut stems close to the ground in July and August.
Japanese knotweed is established throughout Hamilton County, especially along transportation corridors and riparian areas. Cascading flowers bloom in the summer, stems are hollow and notched, and leaves are leathery and heart shaped. It spreads by rhizomes. Manage by applying herbicide to cut stems in early summer and early fall. For more information, visit the Regional Inlet Invasive Plant Program: http://www.noknotweed.org/
Garlic mustard is established throughout Hamilton County, especially in campgrounds. First year plants look like kidney beans that grow low to the ground. Second year plants are erect and can grow to 4 feet. Toothed, triangular flowers give off a garlicky smell when crushed. Tiny white flowers appear in May. It spreads by seeds. Manage by pulling or cutting stems in late spring. In the fall, pull first year plants.
Common Reed Grass
Common reed grass is established throughout Hamilton County, especially along transportation corridors. Plumes are feathery and plants can reach 15 feet high. It spreads by seeds and rhizomes. Manage by applying herbicide to cut stems.
Yellow flag is established in ponds on private property as well as the Siamese Ponds Wilderness that is linked to Hamilton County watersheds. Showy yellow flowers bloom in late spring and early summer. Leaves are sword-shaped and ribbed. It spreads by rhizomes and seeds. Manage by first clipping flowers, then applying herbicide to cut stems. Wear gloves as plant causes skin irritation.