Noxious Weeds

Spotted knapweed, a plant native to Turkey and Central Asia, was first noticed in North America in the sea port of Victoria on Vancouver Island, British Columbia in 1893.  Spotted knapweed spread quickly throughout the Western U.S.  The maps below show how quickly it spread across Montana.  It now has infested more than 5 million acres in Montana and its economic effect in terms of eradication costs and lost productivity is estimated at $20 million dollars annually just in the State of Montana.

How can one plant spread that quickly and in many places be the dominant form of vegation?  The answer is simple--biochemical warfare.  This is not merely the case of another alien species that landed on our shores, but rather a "no-holds barred" direct assault on the integrity of our rangeland.

The roots of spotted knapweed work symbiotically with fungi in the soil to create a powerful toxin.  The toxin exudes from the roots and kills other plants in the area.  The spotted knapweed thrives and after a while the other plants are gone.  It is a common sight in August in Western Montana to see entire mountainsides covered with spotted knapweed in bloom.

How Knapweed Spreads

According to the North Dakota Extension Service, people are the major cause of spotted knapweed spread.   The weed is spread readily in hay and on vehicle undercarriages.  They warn against using hay from roadside ditches, especially along primary roadways.  In North Dakota infestations of spotted knapweed are found primarily along highways, waterways, railroad tracks, pipelines, and recently installed utility lines in the western part of the state.

Non-Technical Reports on the Spotted Knapweed Toxin and Other Research

In the article Wicked Weed of the West in the Smithsonian Magazine, spotted knapweed is described as one of the worst invasive species in the United States and one that uses an offensive chemical weapon.  Ragan Callaway at the University of Montana and Jorge Vivanco at Colorado State University and their co-workers studied how the spotted knapweed releases a poison from its roots and how this toxin kills neighboring plants here in the U.S., but not in Europe and Central Asia where the plant is native.

Scientific Articles on Spotted Knapweed

Spotted knapweed is a serious infestation that is having economic impact on Montana and other Western States.  During the past 8 years research groups at the University of Montana in Missoula and at Colorado State University in Fort Logan have discovered the mechanisms by which spotted knapweed is able to spread so quickly.  See the summary of this research with links to original articles.

Other Local Weeds That are Famous and Poisonous

A local weed is henbane. In the play "Hamlet" by Shakespeare, the King of Denmark was asleep on a bench in his garden when his brother poured extract of henbane in his ear, causing his death.

The Greek philosopher, Socrates, was a vocal critic of the government in Athens during a period in which it had become very autocratic.  As described by Plato in the Phaedo, Socrates was tried, convicted, and condemned to drink a cup of poison hemlock, which caused his death.  This plant is widespread in our area.

Links to Websites with Descriptions and Photos of Noxious Weeds

Montana War on Weeds Todd Breitenfeldt's large website at Whitehall High School on Montana weeds is being moved and should be back soon.

Montana Plant Life Photos of Montana plants and descriptions by Jan Hjalmarsson. CD available.

Online version of Idaho's Noxious Weeds, by Robert H. Callihan and Timothy W. Miller. Idaho weeds.

Colorado Weed Management Association List and photos of Colorado weeds.

Dave's Garden This gardening website tells you how to grow spotted knapweed and that all parts of the plant are poisonous.  Claims that this plant was brought to the U.S. as ship ballast.

Plant database at the U.S. Department of Agriculture Large database with photos and descriptions.

Noxious weeds in the Idaho Panhandle National Forest Weeds in this National Forest.

Common weeds in Alberta Weeds in Alberta forests and plains.

Images of noxious weeds and biological controls Norman E.Rees's Images from the USDA.

Fact Sheets on Spurge, Thistle, and Knapweed 2-4 page facts sheets from Colorado State on some common weeds.  See Range

Weed Images from Pacific Northwest Weed Management Handbook.

Center for Invasive Plant Management Large website at Montana State University in Bozeman.