What plant makes a tumbleweed?

What plant makes a tumbleweed? We were east of Flagstaff recently and the wind was huge and there were tumbleweeds blowing across the road.

A tumbleweed, sometimes called a wind witch, is one of those distinctive symbols of the West.

It is pretty much the skeleton of a Russian thistle, so named because immigrants from Russia and eastern Europe brought it to America in the seeds for wheat and other crops.

Part of its scientific name — Salsola — comes from the Latin word for salt, for which the thistle has a high tolerance.

In its young stages the thistle is a bright green, succulent plant, popular with mice and pronghorns and bighorn sheep. When it matures and dies, the remains break off at the root and blow away with the winds.

As it tumbles along, it disperses seeds, as many as 250,000 per plant. The seeds don't have a protective cover or stored food reserves like most seeds. Instead, each seed contains a coiled, miniature plant in a thin membrane.

The seeds germinate at temperatures as low as 28 degrees.

One reason the Russian thistle is such a successful invasive species is that plowing up the prairie's natural grasses created a vast flat surface upon which the weed could roll along.

E-mail Clay at clay.thompson@ arizonarepublic.com.