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Down the Garden Path

Invasive and Noxious Weeds

The Extension Office and Master Gardener Help desks receive lots of questions regarding invasive and noxious weeds every year. There are major differences in how these weeds and plants are managed from the already existing regulatory legislation in Illinois. In a recent newsletter from the University, these two classifications are discussed.

"The State of Illinois has two "legal" lists of problematic plants that require attention -- Noxious Weeds and Exotic Plants.

The Illinois Noxious Weed Law, set into Illinois Administrative Code, lists 10 weeds that must be controlled on property owned or managed. These weeds have detrimental effects on public health, agricultural crop production, or animal production. This law is under the direction of the Director of the IL Department of Agriculture. Most counties in Illinois have a designated Weed Commissioner for local control authority.

Weeds on this list include Common Ragweed (Ambrosia artemisiifolia), Giant Ragweed (Ambrosia trifida), Marijuana (Cannabis sativa), Musk Thistle (Carduus nutans), Canada Thistle (Cirsium arvense), Kudzu (Pueraria montana, P. lobata), Perennial Sowthistle (Sonchus arvensis), and various sorghums including Johnsongrass (Sorghum halepense) and Columbus grass (Sorghum almum).

The two ragweeds need only to be controlled within the corporate limits of cities, towns and municipalities. All other weeds on the list must be controlled anywhere in Illinois. Noxious weeds must be controlled so they don't produce seeds or any other means for propagating, or totally eradicated using legal means.It should be noted these are outdoor-grown weeds. That's important now with one of the weeds."

"The Illinois Exotic Weed Act, also set into Illinois Administrative Code, is managed by the IL Department of Natural Resources. These non-native plants, when planted, will spread by seeds or vegetative propagules (rhizomes, bulbs, tubers, corms, etc.) and naturalize, degrading natural communities, reducing the value of fish or wildlife habitat, and threatening Illinois endangered or threatened species.

For most of these plants, it's the seeds that have caused these plants to spread, particularly in forested and wooded areas. This law doesn't require the owner or manager of property to remove these plants like the IL Noxious Weed Law. However, do everything to prevent them from spreading, including removing flowers before they set seed. The Act does state you cannot sell or plant these without permission from IDNR.

The following species are on the list. Additionally, and this is crucial, ALL their cultivars are included, no matter who or what says the cultivars are sterile. Any cultivar of these plants CANNOT be legally sold or planted in Illinois without a permit from IDNR. This includes all the so-called sterile purple loosestrife cultivars as well as the Fine-Line® buckthorns.

Included plants include Japanese honeysuckle (Lonicera japonica), multiflora rose (Rosa multiflora), purple loosestrife (Lythrum salicaria), common buckthorn (Rhamnus cathartica), glossy buckthorn (Rhamnus frangula), saw-toothed buckthorn (Rhamnus arguta), dahurian buckthorn (Rhamnus davurica), Japanese buckthorn (Rhamnus japonica), Chinese buckthorn (Rhamnus utilis), and kudzu (Pueraria lobata). Kudzu is the only plant also on the Noxious Weed list. More information on both laws can be found at: and -30-