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Wyoming Natural Diversity Database, UW Extension Release New Thistle Field Guide

May 20, 2022
book cover with photo of thistle on it

The Wyoming Natural Diversity Database (WYNDD) at the University of Wyoming has released a new field guide on Wyoming thistles, designed to assist those who work or recreate outdoors in identifying native and nonnative thistles.

Titled “Wyoming Thistle Field Guide” and published in partnership with UW Extension, the pocket-sized guide features photos and descriptions of all 24 thistles found in the state, including the five noxious invasives.

Author Bonnie Heidel, lead botanist for WYNND, says the purpose of the new publication is to “bring attention to the bane and benefits of thistles.”

The guide is intended for statewide use by weed crews, landowners, educators, land managers and botanists. The keys, designed to guide users through the identification process step by step, are written for nonexperts.

“Some of the most pervasive noxious weeds in the state are invasive thistles,” Heidel says.

If not identified and treated accordingly, invasive thistles can displace native species, degrade habitat quality, impact agriculture and reduce land value.

Native thistles, on the other hand, “provide benefits for wildlife, pollinators and for rangeland health in general,” Heidel says. Bird species and large herbivores, such as elk, also rely on native thistles as a food source.

The big takeaway? Know the difference, Heidel says.

Print copies of the publication can be purchased online for $4.50 plus shipping from UW’s Biodiversity Institute at or the Wyoming Weed and Pest Council at Designed for convenience in the field, the guide features a ruler on the inside cover and sturdy spiral binding.

A free digital copy of the guide is available online at

For additional assistance with plant identification, visit to contact a local UW Extension educator.

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