The CSU Extension in Gilpin County helps mountain residents improve their quality of life by offering a website, classes and programs that provide unbiased, research-based information on forestry, wildfire, wildlife, mountain gardening, noxious weeds and many other issues. Through our 4-H programs, we help youth develop life skills and to become more interested in Science, Technology, Engineering and Math (STEM) learning.
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Native Thistles in Gilpin County

You’ve learned about how bad some thistles can be for our environment. You’re primed and ready to pull or spray. Good for you! But before you target all thistles, remember that there are 20 native thistle species in Colorado, and these play an important role for wildlife. Native thistles should not be killed, because they are not noxious weeds.

How do you tell a native thistle from a noxious thistle?

Generally, if the stand of thistles is very dense or very tall (6’), it is usually noxious.
If you are above timberline and see a thistle, it’s probably native.
Native thistles tend to be short, and are usually only found as individual plants or in very small groups of 2-4 plants.
A thistle with a white flower (the FLOWER, not the fluffy dandelion-like seeds), is probably native.

Pictures of native thistles in Gilpin County

C. canescens

Prairie or Platte thistle Cirsium canescens – native.  This thistle is light pink (or even white). Also note the white line on the bracts. Leaves are blue-green.

Mountain thistle Cirsium scopulorum

Mountain thistle Cirsium scopulorum – native.  Found in subalpine and alpine.

C. scariosum

Meadow or Elk thistle Cirsium scariosum – native.  This thistle can either be stemless (as pictured), or have a short stem.

C. clavatum

Fish Lake/Fringed thistle Cirsium clavatum – native. Note: reddish stem and whitish brown flowers. This is very commonly found in Gilpin County. Flowers are buff-colored.