Invasive weeds have many common characteristics. They are opportunistic, meaning they take advantage of any soil disturbance to claim a foothold. Land that has been overgrazed or grazed inefficiently, roadsides and ditches, and construction areas are vulnerable. What makes a pretty flower becoming a noxious weed is robbing local vegetation of water and soil nutrients and pushing them out. Many of these weeds are dangerous to humans or animals. A garden weed usually requires a simple pull to remove, which isn’t true of the invasive weed–they usually have a complex or deep root system that makes this difficult.
Perennial Pepperweed fits into this description. It originated in southwestern Europe and Asia but has been in the western US for quite a while, often beginning in disturbed and inaccessible land. It grows 2 to 4 feet tall in dense patterns. It loves wetlands and it doesn’t take long for Pepperweed to clog up waterways and reduce the forage value in hay or a pasture, which makes it a real pest at the Malheur National Wildlife Refuge.
Perennial Pepperweed is cruciferous (meaning it’s a cousin to mustard and broccoli). It’s edible for humans and is often featured on wild food websites. In a region of the Himalayas the spring leaves shooting up from the roots are harvested. After boiling and an overnight soak in water the plant is cooked like spinach. It is high in protein, iron, and Vitamins A and C. Humans also dry the plant for home décor use.
Until the flowering stage, the plant is also edible for goats, sheep and cattle. The woody stems then make it undesirable. It is dangerous for horses.
Pepperweed reproduces via seed and the root system, making eradication difficult. Burning will not work in eliminating the weed, though it will remove the thatch. Mowing will stimulate the root system and cause regrowth, so that is not a good choice at all. Repeated and timely applications of herbicide can be successful, but reseeding the area is crucial to ensure it will not return.
(sources Weeds of the West. 9th Edition, copyright 2002, Whitson, et al; and Michael Becker, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=233439)