A native of Russia, thistle seed was mixed in with flax seed, brought into and planted in South Dakota in the 1870s.
Russian thistle tumbleweed (Salsola tragus L. or Salsola iberica) starts to germinate when the soil temperature is slightly warm, around 36 degrees Fahrenheit (F), and the seedling can withstand a frost. In a field study, germination peaked when soil temperatures were 59 to 77 degrees F during the day, and 32 to 41 degrees F at night [1], making this a cool season weed with the capability to germinate extremely fast. Fortunately, seeds are short lived 1 to 2 years on the soil.
Once germinated, it looks just like think leathery green blades of grass. Control may still be achieved while the plant looks like leathery grass with 2-4-D in May. A pre-emergent, like Plateau, may be used in late March to early April. While not a huge advocate of mowing, you may cut this down before it's 6 inches or less in height and achieve some control.
While young, and before branching and thorns form, Russian thistle may be a forage source for livestock and native animals. However, oxalates and nitrates in the tissue of Russian thistle can poison sheep.
Flowering begins in mid-June, and they are inconspicuous and pollinated by the wind. Seed production starts in August.
There are some early research-stage, non-chemical, biological controls for Russian thistle. One is the native caterpillars Coleophora parthenica and C. klimeschiella. Both caused sufficient damage to Russian thistle where they were released in Canada. Coleophora parthenica was also released in the Coachella Valley of southern California--the larvae infested most Russian thistle plants; however, it had little effect there on the growth or thistle population levels. Another control being researched is rust fungus; Uromyces salsolae, the anthracnose fungus Colletotrichum gloeosporioides, and the bare spot fungus Rhizoctonia solani, all have shown potential to suppress growth under controlled conditions.
Russian Thistle pollen is a contributor to summer hay fever problems, another reason to control it when it looks like grass.
So prevalent were tumbleweeds, a song was written in 1930 by Bob Nolan, then made famous by Sons of the Pioneers, "Tumbling Tumbleweeds,"
"See them tumbling down,
Pledging their love to the ground,
Lonely but free I'll be found,
Drifting along with the tumblin' tumbleweeds."
Written by Catherine Wissner, retired University of Wyoming Laramie County Extension Horticulturist and Laramie County Advanced Master Gardener.
[1] "Russian-thistle," Charles L. Mohler, John R. Teasdale, and Antonio DiTommaso, published in Sustainable Agriculture Research and Education (SARE) Handbook Series 16, Manage Weeds on Your Farm: A Guide to Ecological Strategies, page 358, 2019, available for download from www.sare.org/mamage-weeds-on-your-farm
Additional Resources:
"Identification and Management of Kochia and Russian Thistle, CSU Fact Sheet No.6.314," S. Bokan, K. Crumbaker, and G. Beck, Colorado State University Extension