The Maui News / MATTHEW THAYER photo

A large tumbleweed blocks a portion of Pulehu Road recently. The invasive thorny bushes are annual plants that break off at the stem when they dry and distribute seeds as they roll in the wind (up to 250,000 seeds per bush). The type of tumbleweed found on Maui, Russian thistle, is thought to be originally from Eurasia and arrived in the U.S. around 1870, transported in flax seed imported by Ukrainian farmers in South Dakota. After becoming widespread across the western U.S., the noxious weed hitchhiked to Maui, where it has spread to become a costly pest to Kula farmers and a road hazard.