Status of Invasive Plants in Pennsylvania

Invasive Plants by Category

• Aquatic - 11 species, 496 records
• Conifer Trees - 4 species, 82 records
• Forbs/Herbs - 281 species, 15535 records
• Grass or Grasslike - 77 species, 4146 records
• Hardwood Trees - 58 species, 1677 records
• Shrub or Subshrub - 63 species, 2508 records
• Vines - 41 species, 1613 records

Top Ten Abundant Invasive Plants (by number of reports)

1. Japanese stiltgrass - 508 reports
2. Japanese barberry - 321 reports
3. watercress - 287 reports
4. multiflora rose - 282 reports
5. garlic mustard - 217 reports
6. redtop - 201 reports
7. big chickweed - 198 reports
8. bittersweet nightshade - 194 reports
9. barnyardgrass - 190 reports
10. ladysthumb - 187 reports

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

1. yellow toadflax - 67/67 (100%)
2. common St. Johnswort - 67/67 (100%)
3. common ragweed - 67/67 (100%)
4. hedge bindweed - 67/67 (100%)
5. lambsquarters - 67/67 (100%)
6. Queen Anne's lace, wild carrot - 67/67 (100%)
7. hairy galinsoga - 67/67 (100%)
8. common velvetgrass - 67/67 (100%)
9. oxeye daisy - 67/67 (100%)
10. black medic - 67/67 (100%)

Counties with the most invasive species reported

1. Philadelphia County - 501 species
2. Bucks County - 450 species
3. Montgomery County - 437 species
4. Allegheny County - 424 species
5. Berks County - 412 species
6. Northampton County - 411 species
7. Lehigh County - 402 species
8. Chester County - 387 species
9. Delaware County - 381 species
10. Lancaster County - 359 species

Counties with the least invasive species reported

1. Cameron County - 127 species
2. Jefferson County - 136 species
3. Clarion County - 139 species
4. Sullivan County - 141 species
5. Montour County - 142 species
6. Columbia County - 146 species
7. Indiana County - 152 species
8. Forest County - 153 species
9. Union County - 163 species
10. Wyoming County - 163 species