What is a Weed?

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Generally, the term weed can be used for any unwanted plant. Terms such as aliens, exotics, invasives, are used interchangeably to describe a specific weeds. All these descriptions have a common concept: plants introduced into an area in which they did not evolve and cause significant economic and/or ecological impacts.

A noxious weed typically is an official designation of a particular weed within a state.

Wyoming Designated Noxious Weeds .S. 11-5-102 (a)(xi)
and
Prohibited Noxious Weeds W.S. 11-12-104

1. Field bindweed (Convolvulus arvensis L.)
2. Canada thistle (Cirsium arvense L.)
3. Leafy spurge (Euphorbia esula L.)
4. Perennial sowthistle (Sonchus arvensis L.)
5. Quackgrass (Agropyron repens (L.) Beauv.)
6. Hoary cress (whitetop) (Cardaria draba and Cardaria pubescens L.) Desv.)
7. Perennial pepperweed (giant whitetop) (Lepidium latifolium L.)
8. Ox-eye daisy (Chrysanthemum leucanthemum L.)
9. Skeletonleaf bursage (Franseria discolor Nutt.)
10. Russian knapweed (Centaurea repens L.)
11. Yellow toadflax (Linaria vulgaris L.)
12. Dalmatian toadflax (Linaria dalmatica (L.) Mill.)
13. Scotch thistle (Onopordum acanthium L.)
14. Musk thistle (Carduus nutans L.)
15. Common burdock (Arctium minus (Hill) Bernh.)
16. Plumeless thistle (Carduus acanthoides L.)
17. Dyers woad (Isatis tinctoria L.)
18. Houndstongue (Cynoglossum officinale L.)
19. Spotted knapweed (Centaurea maculosa Lam.)
20. Diffuse knapweed (Centaurea diffusa Lam.)
21. Purple loosestrife (Lythrum salicaria L.)
22. Saltcedar (Tamarix spp.)
23. St. Johnswort (Hypericum perforatum L.)