The tumbleweed, a staple of old Western movies and a symbol of the American West to many, is a plant that is not even native to North America. Instead, the tumbleweed is a native of the steppe terrain of Russia, giving rise to another of its common names, Russian thistle. The tumbleweed, according to the Desert USA website, came to South Dakota in seed form by accident in 1877 and then spread across all the western states.
The tumbleweed looks very different when young than it does when it matures. A tumbleweed can grow to 3.5 feet high, and its numerous branching stems will have stripes of purple-red. The leaves on the immature tumbleweed resemble those of a pine tree, almost needle-like in appearance. As the tumbleweed develops, the leaves become narrow and a dark green color and are about one inch long. At this stage of the tumbleweed’s growth, it is a suitable forage plant for livestock such as sheep, cows and horses. The Utah State University Range Plants of Utah site describes the tumbleweed as "soft and succulent" during this phase of its growth.
From July through October, the tumbleweed changes as it matures. The oldest leaves will develop a pointy tip and become stiffened; this helps them to conserve moisture in times of drought. Pinkish to greenish small flowers, which possess no petals, emerge between a pair of modified leaves known as bracts. The University of California Integrated Pest Management website says these features protect the seeds that the flowers bear from hungry birds and animals.
Time to Tumble
By the time a tumbleweed is mature, it can be as small as a foot and a half across or have a width of six feet. The size depends on the growing conditions, with such factors as moisture levels and the quality of the soil playing important roles. The plant will then dry out, and the base of the stem to which the main body of the tumbleweed attaches will break, allowing the dried-up tumbleweed, now looking like a skeleton of itself, to follow the path the winds take it on—a trait that gives the plant its name.
As the wind takes the tumbleweed here and there, the plant will disperse its seeds. The rounded shape allows the tumbleweed to roll wherever the ground is flat or free of obstructions. As the plant rolls, the seeds begin to scatter. A single tumbleweed plant may produce as many as a quarter of a million seeds. You may actually be able to distinguish where a tumbleweed rolled in the spring when the seedlings that it scattered begin to spring up across a field.
Once the temperature and the availability of water cause a tumbleweed seed to germinate, the plant grows quickly. The tumbleweed quickly puts down a lengthy taproot to garner any wetness in the ground. The tumbleweed will not do well in hard ground and typically flourishes in places like vacant lots, along fence lines, along the side of the road and in abandoned fields.