Status of Invasive Plants in Colorado

Invasive Plants by Category

• Aquatic - 4 species, 36 records
• Cactus - 1 species, 5 records
• Forbs/Herbs - 186 species, 7961 records
• Grass or Grasslike - 75 species, 2376 records
• Hardwood Trees - 23 species, 348 records
• Shrub or Subshrub - 20 species, 626 records
• Vines - 13 species, 375 records

Top Ten Abundant Invasive Plants (by number of reports)

1. Canada thistle - 737 reports
2. musk thistle - 643 reports
3. yellow toadflax - 413 reports
4. Dalmatian toadflax - 344 reports
5. diffuse knapweed - 333 reports
6. cheatgrass - 326 reports
7. leafy spurge - 300 reports
8. Russian-olive - 274 reports
9. houndstongue - 269 reports
10. Scotch thistle - 231 reports

Top Ten Widespread Invasive Plants (by number of positive counties)

1. cheatgrass - 63/64 (98%)
2. flixweed - 60/64 (94%)
3. yellow sweetclover - 60/64 (94%)
4. smooth brome - 57/64 (89%)
5. western salsify - 57/64 (89%)
6. crested wheatgrass - 57/64 (89%)
7. Canada thistle - 53/64 (83%)
8. field brome - 52/64 (81%)
9. intermediate wheatgrass - 52/64 (81%)
10. field bindweed - 49/64 (77%)

Counties with the most invasive species reported

1. Boulder County - 286 species
2. Larimer County - 252 species
3. Jefferson County - 216 species
4. El Paso County - 194 species
5. Montezuma County - 192 species
6. Mesa County - 188 species
7. Weld County - 174 species
8. Las Animas County - 159 species
9. La Plata County - 153 species
10. Denver County - 145 species

Counties with the least invasive species reported

1. Phillips County - 30 species
2. Lake County - 31 species
3. Crowley County - 39 species
4. Morgan County - 42 species
5. Washington County - 47 species
6. Bent County - 48 species
7. Prowers County - 53 species
8. Kiowa County - 54 species
9. Otero County - 59 species
10. Summit County - 60 species