Thistles

Stem with Spines, Spiny Plates, or Spiny Ridges
Nodding Thistle Carduus nutans	Welted Thistle Carduus crispus	Scotch Thistle Onopordum acanthium
Bull Thistle Cirsium vulgare	Yellow Thistle Cirsium horridulum
Stem without Spines, Spiny Plates, or Spiny Ridges
Upper Leaves Embracing Flower Head
Pasture Thistle Cirsium pumilum	Field Thistle Cirsium discolor	Swamp Thistle Cirsium muticum
Blessed Thistle Cnicus benedictus	Tall Thistle Cirsium altissimum
Upper leaves not Embracing Flower Head
Canada Thistle Cirsium arvense	Virginia Thistle Cirsium virginianum