The Ravalli County Weed District Posted some information about the spread of Rush Skeletonweed on their Facebook page that sparked a flurry of questions on my page when I shared their post. I will answer some of those questions here.
- Rush skeletonweed is a perennial forb that can grow up to 4 ft. (1.2 m) tall. Coarse-looking, multiple stems that appear leafless due to inconspicuous leaves and arise from a basal rosette of sharply lobed leaves. This plant overwinters as a rosette resembling the dandelion plant which can make it difficult to identify until growth begins again in the spring. The lower 4-6 in. (10.2-15.2 cm) of stem is covered with coarse brown downward pointing hairs.
Both stem and leaves produce a milky latex sap when broken. 
Back in the 1940’s the Russians tried to make rubber out of the sap from this plant. Small yellow flowers begin blooming in early summer (May) and continue until frost in the fall. Mature, healthy plants can produce 1,500 flower heads and up to 20,000 seeds. Seeds are quick to mature (9 to 15 days after the flowers open). Each seed has a parachute of fine hairs which allow it to travel long distances by wind. It has a deep taproot of 8 to 10 feet, with lateral roots, often four feet deep. When its roots are severed, they will produce shoots which can reach the soil surface from depths of 4 feet. Taproot cuttings of 1/2-inch wide and one-inch long can produce new plants. Rush skeletonweed is native to regions of Europe, Asia, and Africa and was thought to have been accidentally brought to the United States as a contaminant of fodder between 1914 and 1938. Rush Skeletonweed was first reported in the U.S. near Spokane, Washington in 1938. It was found in Idaho and Oregon during the 1960’s & 70’s. This weed thrives in well drained, sandy textured or rocky soils, residential properties, along roadsides, in rangelands, semi-arid pastures and grain fields. Basically anywhere the land is repeatedly disturbed can become habitat for this prolific weed.
2. We now have this noxious weed in Ravalli County and have learned a few things about how it spreads and our control options. First of all if you hand pull rush skeleton weed the plant sends out lateral runners and spreads faster as mentioned above. I have included the Ravalli County Weed District photo of the treatment area from 2014 (
green flags) and 2015 (black flags). The weed district could not get permission from the landowner to spray so they pulled the weeds instead and monitored the area. As you can see in the picture below the pulling increased the spread. Our best treatment options at this time are chemical and biological control. Four biological control agents have been released for control of Rush Skeletonweed in North America: a mite, a midge, a rust, and a root-feeding moth (Bradyrrhoa gilveolella), soon to be released in the state of Montana.
3.This noxious weed can be a serious threat to wheat farming since it will spread from undeveloped areas into crop fields. Rush Skeletonweed can foul up harvesting machinery and contaminate the wheat crop. Rush Skeletonweed will also reduce crop yields on farmland by aggressively out-competing for nutrients and soil moisture. In Australia, competition from Rush Skeletonweed reduced wheat yields by as much as 80 percent, resulting in estimated losses of more than $35 million.
There are several great resources for more information which I am listing below. If you think, suspect, believe etc. that you might have this weed on your property please call the Ravalli County Weed District (406) 777-5842 or Landsmith Enterprises (406) 239-4195 for definitive identification, control options and help finding resources. Let’s eradicate this weed in Montana and prevent the spread of Rush Skeletonweed.
http://www.idahoweedawareness.net/vfg/weedlist/rskeletonweed/rskeletonweed.html
http://www.co.lincoln.wa.us/WeedBoard/controloptions/rushskeletonweedoptions.pdf