The Top 20 Least Wanted Species, a list developed by ISN partners in October 2010, consists of those which pose the greatest threat to our region’s high quality natural areas. Half the species listed were imported for landscape use; they may well be living in your own backyard.
| # | Common Name | Latin Name | Category | Photo |
|---|---|---|---|---|
| 1. | garlic mustard | Alliaria petiolata | Agriculture |  |
| 2. | Japanese barberry | Berberis thunbergii | Ornamental |  |
| 3. | oriental bittersweet | Celastrus orbiculatus | Ornamental |  |
| 4. | canada thistle | Cirsium arvense | Weedy |  |
| 5. | European swamp thistle | Cirsium palustre | Weedy |  |
| 6. | bull thistle | Cirsium vulgare | Weedy / Ornamental |  |
| 7. | russian olive* autumn olive* |
Elaeagnus angustifolia Elaeagnus umbellata |
Ornamental |   |
| 8. | leafy spurge | Euphorbia esula | Weedy |  |
| 9. | baby’s breath | Gypsophila paniculata | Ornamental |  |
| 10. | dame’s rocket | Hesperis matronalis | Ornamental |  |
| 11. | lyme grass | Leymus arenarius | Ornamental |  |
| 12. | honeysuckle (multiple species) | Lonicera spp. | Ornamental |  |
| 13. | purple loosestrife | Lythrum salicaria | Ornamental |  |
| 14. | wild parsnip | Pastinaca sativa | Agriculture |  |
| 15. | reed canary grass (aka ribbon grass) |
Phalaris arundinacea | Ornamental / Agriculture |  |
| 16. | common reed | Phragmites australis | Weedy |  |
| 17. | Japanese knotweed giant knotweed |
Polygonum cuspidatum Polygonum sachalinensis |
Ornamental |   |
| 18. | common buckthorn glossy buckthorn |
Rhamnus cathartica Rhamnus frangula |
Ornamental |   |
| 19. | multiflora rose | Rosa multiflora | Ornamental |  |
| 20. | narrow-leaved cattail | Typha angustifolia | Weedy |  |
Categories
Ornamental: Introduced for use in ornamental landscapes.
Weedy: Likely introduced accidently.
Agriculture: Introduced for use as a crop, a cover crop, or forage.