Janesville, WI Invasive Plant Rules: Prohibited Species (2026)

Rather than rely only on the state definitions, the City Council built its own itemized list into Sec. 22-204(a): buckthorn, bull thistle, burdock, Canada thistle, dame's rocket, field bindweed, garlic mustard, goatsbeard, leafy spurge, marijuana, musk thistle, nettle, oxeye daisy, pigweed, purple loosestrife, quackgrass, ragweed, snapdragon, sow thistle, sweet clover, wild morning glory, wild mustard, yellow rocket, and yellow dock are all noxious weeds in the City no matter their height, unlike the general grass and weed rule in Sec. 22-204(b), which only kicks in past 12 inches.

The duty not to permit growth of these species falls on any person who owns, occupies, rents, leases, or controls the property under Sec. 22-204(a), and Sec. 22-205 defines "noxious weed" broadly to include invasive species that are difficult to control or harmful to people, livestock, wildlife, or the environment, expressly folding in the Sec. 22-204 list. None of the 24 species can be preserved as part of a City-approved natural landscape either, since Sec. 22-207(a) only protects "native and beneficial plants" obtained lawfully, and several of the listed species, like buckthorn and purple loosestrife, are well-documented non-native invaders in Wisconsin rather than natives.