The steel thistle was a native Safeholdian plant which looked very much like Earth's bamboo.

The plant bore seed pods filled with small, spiny seeds embedded in fine, straight fibers. The seeds were extremely difficult to remove by hand, but the fiber could be woven into a fabric which was even stronger than cotton silk. It could also be twisted into extremely strong, stretch-resistant rope. Moreover, the plant grew almost as rapidly as actual bamboo, and the yield of raw fiber per acre was seventy percent higher than for terrestrial cotton.

Prior to the introduction of the cotton gin to Safehold by Merlin Athrawes, virtually the only entity capable of producing general market quantities of steel thistle was the Harchong Empire. There, the serfs who lived in de facto slavery could endure the massive difficulty, which included high risk of skin puncture and potentially fatal infection, of hand-removing steel thistle seeds. The cottin gin made previously impossible cheap production of steel thistle sails, rope, and other common material a reality. (OAR)