NOTICE: The WeedUS Database of plants invading natural areas in the U.S. (including Hawaii) has been compiled from a wide variety of sources including publications, reports, surveys, and occasional personal observations from experts in the field. Sources include the National Park Service and other federal agencies, state and local natural resource departments, The Nature Conservancy, state and regional Exotic Pest Plant Councils and related organizations, universities and others. Sources for each plant listed are provided on the table -- click on the REFERENCE(S) header to go to a legend for the source codes. The current list includes over 1,000 plants and is updated as needed. Please contact Jil Swearingen (jil_swearingen@nps.gov) regarding any errors, omissions or potential additions to the list.

The purpose of this list is informational and educational and it is neither intended nor approved for use as a regulatory tool. Many of the species on this list are economically important horticultural plants but sometimes cause problems when they escape and establish in natural areas.

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Download the complete WeedUS Excel file

Plant Conservation Aliance - Alien Plant Working Group's

Alien Plant Invaders of Natural Areas
By Scientific Name
Species beginning with the letter O
SCIENTIFIC NAME COMMON NAME STATES NATIONAL PARKS REFERENCE(S) FACT SHEET
Oenothera glazioviana red sepal evening primrose CA REDW JS Look-up Oenothera glazioviana on USDA PLANTS Volunteer
Oenothera laciniata cut-leaved evening primrose HI HALE JS Look-up Oenothera laciniata on USDA PLANTS Volunteer
Olea europaea ssp. africana African olive HI   UHI Look-up Olea europaea ssp. africana on USDA PLANTS Volunteer
Olea europaea olive CA DEVA FC, JS, TNC Look-up Olea europaea on USDA PLANTS Volunteer
Onopordum acanthium Scotch thistle; Scotch cotton thistle AZ, ID, MO, OR, UT, WA, WY GRCA FC, MODOC, PNWEPPC, JS, TNC Look-up Onopordum acanthium on USDA PLANTS Volunteer
Oplismenus hirtellus brittle basketgrass; honohonokukui HI HALE JS Look-up Oplismenus hirtellus on USDA PLANTS Volunteer
Opuntia ficus-indica tuna cactus; Indian-fig HI HALE JS, TNC Look-up Opuntia ficus-indica on USDA PLANTS Volunteer
Ornithogalum nutans nodding star-of-Bethlehem DC, MD, PA ANTI, CHOH, MDDNR, JS, PADCNR Look-up Ornithogalum nutans on USDA PLANTS Volunteer
Ornithogalum umbellatum star-of-Bethlehem CT, DC, IN, KY, MD, PA, TN, VA, WI, WV ANTI, HAFE, MONO, STRI CIPWG, INPAWS, KYEPPC, MDDNR, JS, PADCNR, WIDNR Look-up Ornithogalum umbellatum on USDA PLANTS Volunteer
Orobanche minor hellroot GA   GAEPPC Look-up Orobanche minor on USDA PLANTS Volunteer
Oxalis debilis var. corymbosa pink wood sorrel; 'ihi-pehu HI HALE JS Look-up Oxalis debilis var. corymbosa on USDA PLANTS Volunteer
Oxyspora paniculata bristletips; oxyspora HI   UHI Look-up Oxyspora paniculata on USDA PLANTS Volunteer

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http://www.nps.gov/plants/alien/list/o.htm
Last updated: 10-Apr-2007