Winged thistle, Carduus tenuiflorus, may exceed 2 meters in height. This is a tenacious weed of roadsides, fields, and disturbed areas.
Winged thistle is a symptom of serious problems with soil health and soil structure. It is present in soils with anaerobic bacteria and where beneficial bacteria can survive well. The soil may be also sticky and acidic.
Exceptionally low Calcium and organic matter levels are also connected to presence of this species of Thistle.