Picture this in your sepia-toned imagination: a lonely, dusty desert street, bleached by the ever-present sun. A couple of tired horses are tied to the wooden hitching post in front of the general store. A vulture circles ominously overhead, and a scrawny yellow dog trots uneasily across the road. If that doesn't build enough ambience for the western movie in your head, add a tumbleweed, freed from its roots by the wind and drought. It half-rolls and half-bounces in the breeze until it lodges against a barbed-wire fence, trapped alongside a half-dozen of its cousins. Now you've got the iconic western setting.
Or do you? That tumbleweed, so evocative of desolate western life, is no more native to the land than the ponies tethered in front of the shop. It's true name is Russian thistle. The bane of sock-wearing hikers who've encountered them in the arid regions of the west, it was an import. You've probably already guessed it came from Russia. It's last name, though, is a misnomer: it's actually not a thistle, despite its prickly nature. If you're a stickler for detail, you'll refer to it by its botanical name: Salsola iberica.
The tumbleweed hitch-hiked here as a stowaway in a load of flax seed shipped to South Dakota. It fit in well, thriving on the harsh, dry conditions -- and, like most of the native desert plants, its stickers made it seem like a natural. It germinates quickly and, thanks to its tumbling skills, it spreads its seed with each bounce. It's considered an invasive weed by some, and a darned nuisance by others.
It didn't arrive in the United States until the 1870's, but it was soon clear it was here to stay. If you're watching movies set earlier in the century, those tumbleweeds rolling along the landscape are anachronisms.