railroad expansion and the development of portable, steam-powered grain thresh- ers. "The destruction of the native prairie grasses enabled the thistle to exploit an ecological niche," Young notes.
Farmers themselves also helped the wind witch to spread. They often unwit- tingly sowed Russian thistle seeds along with their crop seeds, and grain shipments railroad were contaminated. "In addi- tion," Young writes, "the same steam threshermen who so disliked the spiny weed...