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Home :: Weed Department :: Noxious Weeds » Poison Hemlock

Poison Hemlock
Apiaceae (= Umbelliferae), the parsnip family

Background

Poison HemlockPoison hemlock is native to Europe. It contains highly poisonous alkaloids toxic to all classes of livestock and humans. It has poisoned many who have mistaken it for parsley. Poison hemlock is often found on poorly drained soils, particularly near streams, ditches, and surface water.

Description

Poison HemlockPoison hemlock is a biennial that grows up to 10 feet tall. Stems are stout, hollow, ridged, and mottled with purple spots. Leaves are shiny green, 3 to 4 times pinnately compound, and clasp the stem at the obvious nodes. Crushed foliage has a disagreeable, mousey odor. Flowers are small, white, and borne in umbrella-shaped clusters about 3 inches across in early summer. Seeds are ridged and flattened, with 2 seeds borne together. The plant has a thick, white taproot.

Distribution

Poison Hemlock distribution mapIt grows throughout the U.S. except from eastern Montana to northeastern Minnesota and south to Nebraska. It has an extensive presence in Idaho.

Control

A biological control agent (a defoliating moth) provides good to excellent but inconsistent control. Herbicides are also available.

 

© 1999 University of Idaho: Text and photographs for these pages from Idaho's Noxious Weeds, by Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita and Larry W. Lass).

Please contact: Ag Publishing, University of Idaho, Moscow, Idaho 83844-2240; 208 882-7982 visit the Resources for Idaho website at http://info.ag.uidaho.edu, for more information about this or other publications.

 

 

 

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Home :: Weed Department :: Noxious Weeds » Spotted Knapweed

Spotted Knapweed  Asteraceae
(= Compositae), the aster family

Background

Spotted KnapweedSpotted knapweed, native to Europe, is thoroughly established in North America. In Idaho the weed is widely dispersed. Each plant produces up to 25,000 seeds that wind, animals, and people disperse. Seeds may remain viable for 8 years

Description

Spotted knapweed is a biennial or short-lived perennial. Mature plants may be 3 feet tall and are much branched. The weed forms a basal rosette the first year with leaves up to 6 inches long; both basal and stem leavesSpotted Knapweed are pinnately divided. Flower heads are abundant, 1/2 inch wide, and solitary on branch tips. Flowers are pink to purple, or occasionally white, and appear from midsummer to fall. Each stiff flower head bract has a dark comblike fringe resembling a black spot at the tip. Seeds are dark brown to tan and are tipped by plumes that falloff at maturity.

Distribution

Spotted Knapweed distribution mapSpotted knapweed is found in the northeast and north central U.S. as well as along the Pacific Coast, most of Idaho, and east through Montana.

Control

Several biological control agents are available. A seed head moth and 2 seed head gall flies have been effective. Herbicides are available for control of spotted knapweed.

© 1999 University of Idaho: Text and photographs for these pages from Idaho's Noxious Weeds, by Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita and Larry W. Lass).

Please contact: Ag Publishing, University of Idaho, Moscow, Idaho 83844-2240; 208 882-7982 visit the Resources for Idaho website at http://info.ag.uidaho.edu, for more information about this or other publications.

 

 

 

-- Home :: Commissioners :: Departments :: Judicial ::Services ::  Links --

-- Commissioners' Proclamation --
-- Terms of Use --
--  Site Map --

©2010 Minidoka County, Idaho
- Web Site by Surf The Snake -