Mousillon Rose

The Mousillon Rose is a plant that grows in the hills of said-duchy. This bush has luxuriant evergreen leaves and vivid purple flowers that bloom most of the year. It looks out of place in the hills, but it fits right in. The stems are coated with vicious, barbed thorns, and the pollen is a deadly poison. What is more, it grows where a human corpse has been left to rot. The sites of old battles are known to turn into thickets of the deadly plant.

Source
1: Warhammer Fantasy RPG 2nd ED: Knights of the Grail
 * 1a: pg. 81 - 83