Tamarisk Infestations


Fighting Tamarisk Infestations
on the South Platte River

Ken A. MacKenzie
Engineering Inspector, South Platte River Program

Tamarisk, also known as saltcedar for the salty oil exuded by its leaves, was first introduced into the western United States in the late 1800's as an ornamental tree and windbreak. A prolific seed producer (a single plant may produce hundreds of thousands of viable seeds annually) it quickly escaped cultivation and now thrives in riparian corridors throughout the west.

Recognized as a noxious weed by many states, including Colorado, this highly invasive Eurasian evergreen has reddish brown bark, a light green feathery leaf appearance, and tiny pink flowers. This plant has virtually no wildlife habitat value and develops impenetrable coppices, blocking river access to wildlife while choking out willows, cottonwoods, and other desirable native vegetation.

Several infestations of tamarisk were targeted for eradication along the South Platte River in Adams County this fall. They were found in the area north of 88th Avenue and east of Riverdale road. This area of gravel pit lakes had provided the tamarisk an ideal growth environment and it had spread from the lakes to the lower banks on both sides of the river.

The District's routine maintenance contractor, RBI Maintenance, Inc. was given the task of removing approximately 9,500 plants from district easements on both sides of the river. With a crew of 4 laborers and a licensed herbicide applicator, RBI spent 150 man-hours cutting down and hauling away the tamarisk. Using a backpack spray applicator, each stump was treated with a solution of 1 part Garlon(r) 4 to 3 parts water, with a fluorescent blue dye added to ensure thorough application.  Close monitoring and follow-up maintenance of these sites will be necessary for years to come. We anticipate a 10% regrowth from the cut stumps, and an additional 10% occurrence of seedling plants in 1999 alone. As long as tamarisk is prevalent on adjacent properties, the South Platte River will be subject to new infestations of this insidious and detrimental weed.

We thank the following individuals for their guidance and advice on this project:

Dr. K. George Beck, Associate Professor of Weed Science, Extension Specialist, Colorado State University
Carl Zimmerman, Bent's Old Fort Park Ranger & Living History Interpreter, National Park Service
Mary L. Powell, Natural Resource Specialist, ERO Resources Corp.


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