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Description:Leafy spurge is an erect, branching, perennial herb 2 to 3.5 feet tall, with smooth stems and showy yellow flower bracts. Stems frequently occur in clusters from a vertical root that can extend many feet underground. The leaves are small, oval to lance-shaped, somewhat frosted and slightly wavy along the margin.
Leafy spurge is an ecological threat. It displaces native vegetation in prairie habitats and fields through shading and by usurping available water and nutrients and through plant toxins that prevent the growth of other plants underneath it. Leafy spurge is an aggressive invader and, once present, can completely overtake large areas of open land.
Life History:Leafy spurge reproduces readily by seeds that have a high germination rate and may remain viable in the soil for at least seven years, enhancing its chances of recovery over time. Its seed capsules open explosively, dispersing seed up to 15 feet from the parent plant and may be carried further by water and wildlife. Leafy spurge also spreads vegetatively at a rate of several feet per year. The root system is complex, can reach 15 or more feet into the ground, and may have numerous buds.
Habitat:In the United States, leafy spurge tolerates moist to dry soil conditions but is most aggressive under dry conditions where competition from native plants is reduced. It is capable of invading disturbed sites, including prairies, savannas, pastures, abandoned fields and roadside areas.
Distribution:
Leafy spurge occurs across much of the northern U.S., with the most extensive infestations reported for Montana, North Dakota, Nebraska, South Dakota, and Wyoming. It has been identified as a serious pest on a number of national parks and on preserves of The Nature Conservancy in eleven northern states.
Each year numerous plant and animal species disperse from their natural range to new locations around the world. Invasive species include all taxa of organisms from large mammals to microscopic insects. Many of these non-native, exotic species have colonized the mountain and grassland regions of the United States and become invasive, displacing native plant and animal ecological communities. The consequences of these invasions may be localized or widespread and impacts can range from minor to severe. Invasive species compete with native species, alter ecosystems, and may bring disease not only to native flora and fauna but to humans as well. Many federal, state, tribal, and local governments as well as non-governmental organizations are working to address this issue.
The Global Invasive Species Database defines an alien invasive species as "an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity." The diverse habitats of the northwestern U.S. provide favorable conditions for many invasive animals, microorganisms, and plants. More information about each group of invasive species is presented below.
Invasive Animals Invasive animals negatively impact native animals and ecosystems. In addition, they cause economic harm through increased management and control costs, loss of recreation opportunities, and loss of valuable services provided by stable, functioning ecosystems.
Invasive Viruses and Bacteria Invasive viruses and bacteria of the region include the Avian Influenza Virus and Sudden Oak Death, pathogens affecting both animals and agriculture. Because microorganisms spread easily, invasive viruses and bacteria found in other parts of the nation such as Viral hemorrhagic septicemia could likely expand into this region.
Invasive Plants Invasive plants can disrupt native ecosystems by outcompeting native plants. This change in the structure of native ecosystems can result in loss of habitat and food for other organisms. Because some non-native plants are not as resistant to fire as native plants, many non-native plants can also alter the effects of fire. Highly flammable invasive plants such as Cogongrass and Cheatgrass change natural wildfire from low-intensity, beneficial fire to a high-intensity fire that is difficult to control, damages soil structure, and burns at temperatures higher than native plants can survive.
Additional Resources
Large Zebra Mussel Cluster [Photo: US Fish and Wildlife Service]
With enormous environmental, economic, and health costs, invasive species are second only to habitat destruction as a cause of global biodiversity loss.
Invasive Species of the Week (IUCN Invasive Species Specialist Group - ISSG)
Click on the button below to open a PDF file of a fact sheet for the 'Invasive Species of the Week'.
The ISSG has launched this 'Invasive Species of the Week' button to raise awareness of the impacts of invasive species on native biodiversity and threatened ecosystems. For information about how to add this button to your own Web site, contact Shyama Pagad (Manager, Species Information Services, IUCN SSC ISSG).
The NBII Program is administered by the Biological Informatics Program of the U.S. Geological Survey
![Bull Frog, Dogwood anthracnose, Nutria, Purple Starthistle, Flathead Catfish [Photos: Bill Eonard, USGS; USDA; Justin Secrist, Washington Department of Fish and Game; Malcolm Storey; Eric Engbretson, Fish and Wildlfie Service]](https://cybercemetery.unt.edu/archive/nbii/20120113021658im_/https://www.nbii.gov/portal/server.pt/gateway/PTARGS_0_2_25206_1883_6943_43/http%3B/cbi-lap7.cbi.cr.usgs.gov%3B7097/publishedcontent/publish/geographic/pacific_northwest/pnwin_invasive_species_intro/invasives3.jpg)
