| Rating | Plant Name | Thumbnail |
| 1 | Sea Thistle, Japanese Thistle, Plumed Thistle
Cirsium japonicum |  |
2  | Bull Thistle, Yellow Thistle, Purple Thistle, Spiny Thistle
Cirsium horridulum |  |
| 3 | Yellowspine Thistle
Cirsium ochrocentrum | No Images Yet |
| 4 | Wavyleaf Thistle, Wavy-Leafed Thistle
Cirsium undulatum |  |
| 5 | Tall Thistle
Cirsium altissimum |  |
6  | Canada Thistle, Creeping Thistle
Cirsium arvense |  |
| 7 | Bull Thistle, Spear Thistle
Cirsium vulgare |  |
| 8 | Field Thistle
Cirsium discolor |  |
| 9 | Melancholy Thistle, Curly Head
Cirsium heterophyllum |  |
| 10 | Texas Thistle
Cirsium texanum |  |
| 11 | Swamp Thistle
Cirsium muticus | No Images Yet |
| 12 | Nutall's Thistle
Cirsium nuttallii |  |
| 13 | Rose Thistle
Cirsium andersonii | No Images Yet |
| 14 | Clustered Thistle
Cirsium brevistylum | No Images Yet |
| 15 | Prairie Thistle
Cirsium canescens | No Images Yet |
| 16 | Carolina Thistle, Purple Thistle, Soft Thistle
Cirsium carolinianum |  |
| 17 | Whitespine Thistle
Cirsium clokeyi | No Images Yet |
| 18 | Peregrine Thistle
Cirsium cymosum | No Images Yet |
| 19 | Dwarf Thistle
Cirsium drummondii | No Images Yet |
20  | Cobweb Thistle, Cobwebby Thistle, Red Thistle, Venus Thistle
Cirsium occidentale | No Images Yet |
| 21 | Snowy Thistle
Cirsium pastoris | No Images Yet |
| 22 | Steen Mountain Thistle
Cirsium peckii | No Images Yet |
| 23 | Pitcher's Thistle, Sand Dune Thistle
Cirsium pitcheri |  |
| 24 | Pasture Thistle
Cirsium pumilum | No Images Yet |
| 25 | Alameda County Thistle
Cirsium quercetorum | No Images Yet |
| 26 | Mt. Tamalpais Thistle
Cirsium amblylepis | No Images Yet |
| 27 | Barneby's Thistle
Cirsium barnebyi | No Images Yet |
| 28 | Fish Lake Thistle
Cirsium clavatum | No Images Yet |
| 29 | Rosette Thistle
Cirsium congdonii | No Images Yet |
| 30 | Slough Thistle
Cirsium crassicaule | No Images Yet |
| 31 | Douglas Thistle
Cirsium douglasii | No Images Yet |
| 32 | Queen Thistle
Cirsium chellyense | No Images Yet |
| 33 | Edible Thistle
Cirsium edule |  |
| 34 | Cainville Thistle
Cirsium calcareum | No Images Yet |
| 35 | Ashland Thistle
Cirsium ciliolatum | No Images Yet |
| 36 | Palouse Thistle
Cirsium brevifolium | No Images Yet |
| 37 | Jeweled Thistle
Cirsium araneans | No Images Yet |
| 38 | Hall's Thistle
Cirsium hallii | No Images Yet |
| 39 | Navajo Thistle
Cirsium navajoense | No Images Yet |
| 40 | Longstyle Thistle
Cirsium longistylum | No Images Yet |
