Status of Invasive Plants in Maine

Invasive Plants by Category

• Aquatic - 6 species, 39 records
• Conifer Trees - 3 species, 24 records
• Forbs/Herbs - 224 species, 4106 records
• Grass or Grasslike - 52 species, 875 records
• Hardwood Trees - 34 species, 674 records
• Shrub or Subshrub - 39 species, 1450 records
• Vines - 23 species, 456 records

Top Ten Abundant Invasive Plants (by number of reports)

1. Japanese knotweed - 275 reports
2. multiflora rose - 228 reports
3. Japanese barberry - 202 reports
4. oriental bittersweet - 189 reports
5. Morrow's honeysuckle - 171 reports
6. exotic bush honeysuckles - 153 reports
7. purple loosestrife - 149 reports
8. glossy buckthorn - 145 reports
9. reed canarygrass - 107 reports
10. bittersweet nightshade - 96 reports

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

1. Norway maple - 16/16 (100%)
2. common chickweed - 16/16 (100%)
3. common mullein - 16/16 (100%)
4. bull thistle - 16/16 (100%)
5. Japanese knotweed - 16/16 (100%)
6. yellow toadflax - 16/16 (100%)
7. common St. Johnswort - 16/16 (100%)
8. orange hawkweed - 16/16 (100%)
9. meadow hawkweed - 16/16 (100%)
10. orchardgrass - 16/16 (100%)

Counties with the most invasive species reported

1. Cumberland County - 326 species
2. York County - 317 species
3. Penobscot County - 277 species
4. Knox County - 272 species
5. Hancock County - 265 species
6. Oxford County - 262 species
7. Waldo County - 245 species
8. Kennebec County - 237 species
9. Lincoln County - 215 species
10. Androscoggin County - 210 species

Counties with the least invasive species reported

1. Piscataquis County - 152 species
2. Washington County - 184 species
3. Sagadahoc County - 197 species
4. Franklin County - 206 species
5. Aroostook County - 208 species
6. Somerset County - 209 species
7. Androscoggin County - 210 species
8. Lincoln County - 215 species
9. Kennebec County - 237 species
10. Waldo County - 245 species