Native Thistles: A Conservation Practitioner’s Guide. Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunites

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Native thistles are a largely misunderstood and wrongly maligned group of wildflowers. These diverse plants fill a variety of significant niches along more esteemed wildflowers including the coneflowers, prairie clovers, camas, and compass plant. While so many of those native wildflowers have been embraced by restoration practitioners, ultimately finding a place in our gardens and restored natural areas, appreciation for our native thistles never really caught on. This is too bad. With sublime blue-green foliage, interesting stem and leaf architecture, and pink blossoms, our native thistles are every bit as resplendent as countless other native plants. <br>

More significantly, these plants play important roles in our ecosystems. In great grasslands and prairies, alpine meadows and silty Midwestern river bottoms, the seeds of our native thistles help sustain enormous flocks of songbirds such as goldfinches and indigo buntings. The nectar of these plants fills the stomachs of countless flower visitors, including the enormous black and gold bumble bee (Bombus auricomus), while the foliage of thistles feeds both people and rare butterflies alike. Edible thistle (Cirsium edule), for example, is a staple food of the Salish people of the Pacific Northwest, while swamp thistle (C. muticum) is a caterpillar host plant for the endangered swamp metalmark butterfly (Calephelis muticum). <br>

As with so many of our other native prairie and meadow species, thistles have been a direct casualty of habitat loss, first beginning with the conversion of native plant communities to intensive plow-based agriculture, then continuing with urbanization and the development of cities and roads. Most significantly, the later invasion of non-native thistles and the lack of discernment between superficially similar native and invasive species is heralding the potential end of these beautiful and important plants. A number of native thistles are now threatened with extinction. <br>

In fact, in response to the spread of exotic invasives such as Canada thistle (C. arvense), expansive biocontrol programs have released alien thistle-eating insects that devour invasive and native thistles alike. These biological control efforts have had only limited impacts on some invasive thistles, but likely devastating impacts on our native ones. This pressure has been compounded by farm-level thistle eradication efforts, including the ever-increasing use of herbicides. And, finally, some broad-reaching weed control policies treat all members of the genus as noxious weeds, ignoring the potential to push historically common native thistles toward local extinction. <br>

We think it’s time to bring back native thistles. <br>

This book is our first step in that process. Here you will find one of the most comprehensive discussions of the value of native thistles for pollinators and other wildlife, as well as a detailed account of the conservation status of native thistles, many of which are well studied. Given the significance of non-native thistle invasions and the ramifications this has had for their native counterparts, we provide a brief history of invasion by Canada thistle. Finally, we have developed a practical section on the production of native thistle seed for use in restoration projects. This section is based on multiple years of actual native thistle seed production by the Xerces Society Pollinator Conservation Program in partnership with a fantastic group of native seed companies. <br>

Ultimately we hope this document provides the inspiration and the tools necessary for you to take the next step and make native thistle conservation a routine part of your work—whether you are a public land manager, a native seed producer, or a landowner working to create a conservation legacy. <br>

Native plants are the foundation of a resilient and healthy world. These plants have co-evolved with our pollinators and herbivores, and adapted to their unique corner of the world over tens-of-thousands of years. Native plants provide food for wildlife, sequester carbon in soils, protect water quality, and add color and beauty to our lives. <br>

Ultimately, the inclusion of native thistles in this equation will require a larger paradigm shift on the part of the public and policy makers. You can be a part of that paradigm shift. Along the way there will be much work to do, but also incredible opportunities, not the least of which is the potential to create a new place in our landscapes for the countless wildlife species that are intertwined with this interesting group of plants. For your contribution to this noble cause, we are profoundly grateful. <br>

Notes:

Reference Code: B17ECK01IDUS <br>

Full Citation: Eckberg, J., E. Lee-Mäder, J. Hopwood, S. Foltz Jordan, and B. Borders. 2017. Native Thistles: A Conservation Practitioner’s Guide. Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunites. 92 pp. Portland, OR: The Xerces Society for Invertebrate Conservation <br>

Location: ELECTRONIC FILE - BOTANY: MULTIPLE SPECIES <br>

Keywords: Cirsium, thistle <br>

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Native Thistle Conservation Guide, Xerces 2017.pdf