KC Weeds News - January 2006

TOPICS BELOW

• Weed of the Month: Milk Thistle
• King County Weed Board to Adopt 2006 Noxious Weed List
• New Aquatic Pesticides Permit from Department of Ecology
• New Resource for Gardeners with Weedy Ornamentals
• Favorite Factoid
• News and Links
• Funding Opportunities for Invasives Projects

Weed of the Month: Milk Thistle, Class A Noxious Weed

As every pasture owner knows, thistles are no laughing matter. And milk thistle is one of the nastiest to deal with. It’s 6 feet tall and spiny and forms imposing, dense mounds. A single plant has over 6,000 seeds and they remain viable for over 9 years. It can also poison livestock when they eat enough of it because it is a nitrate accumulator. Large rosettes up to 3 feet across grow over the winter and crowd out grasses and other forage plants, drastically reducing the productivity of the pasture. Even though this thistle is “just” an annual, don’t be fooled. The seeds are long-lived and the plants are tough to kill by any method.

Most milk thistle is found in Oregon and California. However, there are about 30 infestations in pastures in the Enumclaw area and, unfortunately, most of these properties have cattle and most of the infestations are large and well-established. In fact, it is likely that the milk thistle originally came from contaminated hay brought in from out of state. In spite of the hard work of the property owners (and the help of our weed specialists), this thistle just won’t go away. Even more frightening, it was found spreading to new properties after last year’s mild winter and sunny summer. Cleary, more persistence and hard work will be needed to stop milk thistle from taking hold in our state.

Milk thistle is one of the easiest thistles to identify thanks to distinctive white marbling on the leaves that is obvious even on tiny seedlings. Also, both the leaves and the large pink flower heads are armed with stiff spines that are extremely painful to encounter. Although it is now illegal to sell or grow milk thistle in Washington State, it has been used in gardening and is also an important medicinal plant, so it is occasionally found in landscaping or backyards. However, everyone should remove this plant before it seeds to stop it from spreading into more areas of the county and state. The heavy seeds are moved mostly by people, animals and equipment so it is important to monitor areas that are newly planted or where animals are grazing.

If you see any milk thistle growing in the county, please contact us right away so we can work quickly to eradicate it before it spreads any further. Even now, rosettes are ready and waiting to start growing again as soon as the sun appears in the spring.

If you have any concerns about milk thistle or find any new infestations, please contact us at noxious.weeds@kingcounty.gov, use our online form or call us at 206-296-0290.

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King County Weed Board to Adopt 2006 Noxious Weed List

Everyone is invited to the annual King County Weed Board public meeting to review and update the King County Noxious Weed List on Wednesday, January 11, at the Mercer Island Library on Mercer Island, from 4 p.m. to 6 p.m.

The King County Noxious Weed List places a priority on preventing new infestations of the most serious noxious weeds and encouraging all property owners to work together in stopping the spread of established noxious weeds. Here are some of the proposed changes to the county weed list that the Weed Board will consider at the upcoming meeting:

• Adding two new Class A Weeds: reed sweetgrass (Glyceria maxima) and floating primrose-willow (Ludwigia peploides). Both of these plants threaten wetlands and waterways. Both species were added by the State Weed Board as Class A weeds so control is required by all county weed boards automatically.
  
• Reed sweetgrass is not currently present in King County but has spread quickly in a small lake in Snohomish County and is also toxic to livestock. http://tncweeds.ucdavis.edu/alert/alrtglyc.html

• Floating primrose-willow is only present in one place in the state, on a small tributary of the Cedar River in east King County. This fast-growing, creeping aquatic perennial is highly invasive and difficult to control. It chokes out natives and hinders activities such as boating and irrigation. The dense above-water growth can also be a home for nuisance and disease-bearing insects. http://plants.usda.gov:8080/plants//profile?symbol=LUPE5

• Adding two new plants to the county “obnoxious weed” list: hedge bindweed (Calystegia sepium) and yellow archangel (Lamiastrum galeobdolon) These plants are not regulated by the State Noxious Weed Law but adding them to the county list would recognize them as invasive plants and would encourage people to remove them where possible. Hedge bindweed is an aggressively spreading vine that smothers other vegetation and is highly difficult to control once it is established. Yellow archangel has been found spreading into natural areas and forests and is capable of out-competing native forest wildflowers and groundcovers. Both plants spread from even small fragments and should never be discarded into parks or natural areas.

• Expand the county-selected area for required control of Scotch broom (Cytisus scoparius) to include Highway 2 in addition to I-90 east of Mile Post 34. Scotch broom is highly invasive and widespread throughout the county and property owners are encouraged to control it where possible but not required to do so, except along the stretches of state highway that lead over the pass in order to prevent the spread into eastern Washington where this plant is just beginning to invade.

For more information, call Sasha Shaw at the King County Noxious Weed Control Program, 206-296-0290 or email the program at noxious.weeds@kingcounty.gov.

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New Aquatic Pesticides Permit from Department of Ecology

Aquatic weed control may cost more for some projects and take more time to get permits under the proposed changes from the Department of Ecology. Comments are being accepted for the proposed changes until January 20 and there are three public meetings on the proposals coming up in January. See Ecology’s news release for details: http://www.ecy.wa.gov/news/2005news/2005-292.html. For more information on how the proposed changes will affect aquatic noxious weed control projects in King County, please call Roy Brunskill or Steve Burke at 206-296-0290 or email the program at noxious.weeds@kingcounty.gov.

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New Resource for Gardeners with Weedy Ornamentals

A task force led by the Washington Invasive Species Coalition and including our program, the Whatcom County Weed Board and the State Weed Board are working on a new guide for gardeners that provides alternatives for ornamentals that are invasive in the Puget Sound Region. It will feature information and color photos for both the invasives and the alternatives. It should be available in time for the NW Flower and Garden Show and will be distributed to nurseries and coalition organizations in time for the gardening season. In the meantime, check out WISC’s website for alternatives to a few of these problem plants (http://invasivespeciescoalition.org/GardenPlants/InvasivePlants). Also see WISC coordinator Seth Cool’s recent column in the Seattle Post-Intelligencer: http://seattlepi.nwsource.com/opinion/253714_invade29.html

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Favorite Factoid

A 2005 General Accounting Office report on invasive weeds estimates that federal agencies annually spend about $40 million for weed control activities on non-agricultural lands and that 47 million acres of federal lands are infested with invasive weeds. In the United States as a whole, 133 million acres of non-agricultural lands are impacted by invasive weeds. The GAO calls the spread of invasive species “an explosion in slow motion”.

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News and Links

• Massachusetts bans the sale of invasive ornamentals: http://www2.townonline.com/harwich/localRegional/view.bg?articleid=400335&format=&page=1

• It looks like native plant diversity is not necessarily a good defense against invasive plants after all. Check out the article “The Rich Get Richer: Patterns of Plant Invasions in the United States” at http://www.nrel.colostate.edu/projects/stohlgren/index.html (look for this title in “Publications”).

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Funding Opportunities for Invasives Projects

CIPM Grants for invasives research and Cooperative Weed Management Area’s:http://www.weedcenter.org/grants/rfp.html (this site also has links to other funding sources, information on Weed Management Areas and tips for grant writers).

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Back Issues of KC Weeds News

August 2005
June 2005
May 2005

Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact a staff member at the King County Noxious Weed Control Program, please call 206-296-0290 or by reach them by email.

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