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

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 – native.  Found in subalpine and alpine.

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

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.