New invasive weed species found in Lewis and Clark County

Rush Skeletonweed
Posted at 4:25 PM, Sep 05, 2023

HELENA — The Montana Department of Agriculture has confirmed a previously unseen invasive weed in Lewis and Clark County.

Rush Skeletonweed has been confirmed at two different sites outside of Helena.

The plant is considered a Montana Priority 1B Noxious Weed, has limited presence in Montana and if found requires eradication or containment and education.

According to MDA, this is currently the only population of Rush Skeletonweed east of the Continental Divide in the state. The invasive weed can reduce crop yields by as much as 70 percent once established, which is why establishment prevention in central and eastern Montana is critical.

How to identify the plant

Rush Skeletonweed is branched with few or no leaves, giving it a “skeleton-like” appearance. The rosettes look identical to dandelions and once bolted, the stems have stiff downward pointing hairs at the base. Flowers are yellow, smaller than a dime, appear in late summer, and when seeded, have tufted white hairs that disperse in the wind. All plant parts exude a milky latex when broken.

The plant can invade rangeland, farmland, roadsides and even neighborhood yards. It can easily be confused with tumble mustard (, which has small four-petaled pale yellow flowers, and the native rush skeleton-plant, which has no hairs at the stem base, does not contain milky sap, and has pinkish flowers.

Report Rush Skeletonweed

Rush Skeletonweed is difficult to control and harmful to both agriculture and wildland habitat. There are currently 6.2 million acres of Rush Skeletonweed in the western United States, including 4 million acres in Idaho. While Montana currently only has around 3,300 acres, it is critical to keep it from spreading and to eradicate new infestations when found. To report a suspected Rush Skeletonweed plant, submit a report on EDDMapS and contact your local county weed coordinator or the Montana Department of Agriculture Noxious Weed EDRR Program at For additional resources and contact information, visit the Early Detection, Rapid Response webpage here: