“Deep in my heart is a song
Here on the range I belong
Drifting along with the tumbling tumbleweeds”
They are an iconic part of old Western movies, and they are the focus of songs such as “Tumbling Tumbleweeds” by Sons of the Pioneers, the group that launched the career of Roy Rogers.
But early species of tumbleweeds are not a native part of the landscape of the American West. In fact, they are invasive plants that hitchhiked to the United States in the 1800s — and remain a unique landscape pest to much of the Plains and Western states.
“The seeds arrived in grain imported from Russia (eastern Asia) by immigrant farmers in the western United States,” says David Salman, Chief Horticulturist for High Country Gardens in Santa Fe, New Mexico. Contaminated flaxseed was to blame. Upon arrival, the shrubby plants proved they excelled at one thing — seed dispersal.
Bright green and succulent when growing, tumbleweeds have reddish or purple shoots and green flowers accompanied by spiky bracts. Small rodents and antelope might eat the tender shoots, but once the plant has dried to a skeletonized ball of branches, it rarely becomes the breakfast of animals.
Origin of Tumbleweeds in the U.S.
Tumbleweeds sprouted easily when the early farmers planted the infected grain, thriving in cleared areas of land and able to survive on very little water. They had few predators and offered little to farmers as a viable crop. “Since the plant did not appear in North America until the 1870s, native Americans have had relatively little time to discover a use for it,” says Lincoln Smith, a research entomologist with the USDA’s Agricultural Research Service. “Cattle will graze it when the plants are young (before the leaves get spiny), but it tends to cause diarrhea. During the Dust Bowl period in the 1930s, it was used as forage hay out of desperation when grasses failed.” The plant also contains nitrates and soluble oxalates in levels that are poisonous to sheep.
By the early 1890s, the Russian thistle had covered an area of approximately 35,000 square miles over a 20-year period.
It created such an alarm that in 1894, the U.S. Department of Agriculture dispatched botanist Lyster Hoxie Dewie to investigate. He reported that the weed posed an existential threat to farms. “Spreading rapidly as it is over new territory and becoming more destructive in the region already infested, it threatens serious consequences unless prompt measures are taken to subdue it,” Dewie wrote.
The Main Tumbling Culprit: Russian Thistle
Dewie was writing in particular about the Russian thistle. Although there are many species of tumbleweeds, Russian thistle is probably the best known. The Russian thistle plant dies and dries out in the late fall and winter, and its stem snaps off at the roots. Once mobile, it rolls on the slightest breeze. As tumbleweeds tumble, they disperse seeds. One plant can spread approximately 250,000 seeds each winter.
Other species of tumbleweeds found in North America are:
Barbwire Russian thistle (Salsola paulsenii) is found in desert areas. Sand usually anchors down this tumbleweed variety, preventing them from tumbling. Their seeds detach and are scattered by the wind.
Prickly Russian thistle (Salsola australis) is a native to Australia. It is found in areas of California, Arizona, Texas and Hawaii.”It typically does not tumble, and the seeds easily blow off the plant,” says Smith. “Its first appearance in California was probably in the 1980s, and is likely still spreading.”
Two hybrid species, Salsola gobicola (a polyploid hybrid of S. tragus and S. paulsenii) and Salsola ryanii (a polyploid hybrid of S. tragus and S. australis) have intermediate characteristics of the two “parental'”species. The latter hybrid grows later that the other species of tumbleweed. It takes advantage of summer rain and climate changes to grow faster and range farther than the others. It also grows larger — up to 6 feet across.
Like Dewie more than a century before, scientists sound alarms about the new hybrid. “Monster Hybrid Tumbleweed Species Is Taking Over California, Scientists Warn,” said Newsweek magazines in an August 2019 story.
These tumble weed species are annual plants. The seeds germinate in the spring, flowering in the summer or fall, depending on the species. They reproduce only by seed.
When Tumbleweeds Attack
Tumbleweeds are not only useless to farmers and ranchers, but sometimes the rolling plants can be a hazard. They pile up against fence gates, buildings, vehicles, or each other. They become tangled in electrical lines and clog water treatment plants. In 1989, the town of Mobridge, Utah, had to call in equipment operators to remove tumbleweeds that buried homes and created fire hazards.
And in 2018, overgrown areas of tumbleweeds overcame the town of Victorville, Calif.
“Tumbleweeds are primarily a problem where the soil has been severely disturbed by construction, poor farming practices and road building,” says Salman. ” It is a pioneer plant that thrives in conditions too hot and dry for most plants to grow. Generally, this weed is a nuisance. It can pile up along walls and fence lines sometimes to depths of 6 feet or deeper.”
Pollen Woes, Too
The pollen of the Russian thistle is an allergen to some, as well. The spiny tips of the Russian thistle have been known to puncture the skin of both humans and animals and become infected. “In California’s Central Valley, tumbleweeds aid several insect pests of many vegetable crops (the beet leafhopper, Say’s stinkbug, and lygus bug) because these insects feed on tumbleweed in the late summer, when there is nothing else to feed on,” says Smith.
Smith and researchers at the USDA AGR are working on the discovery and evaluation of possible biological control agents of the Russian thistle. A 2014 study uncovered two fungal pathogens that may help. Infected plants in Russia and Hungary both contained the same pathogens Although they eliminated Russian thistle from sites in only two seasons, approval for use of the pathogen has rolled more slowly than the invasion of the plant on land in the Western states. Some herbicide, including glyphosate, might work if it is applied to plants prior to drying and tumbling — though glyphosate, the active chemical in Roundup and other weed-killers, has environmental concerns. For now, the best way to control tumbleweed growth is to remove or completely kill young seedlings as they emerge in the spring.
Before they become the latest horror movie.