Leave the Wavyleaf: Native Vs. Invasive Thistle
By Margaux Klingensmith | August 9, 2024
If you look closely at the sagebrush speckling the northern section of Swaner Preserve you may notice more than meets the eye. While the late summer blooms may not be as flashy as spring displays, wildflowers still flourish into autumn. Plants such as Red-root Buckwheat, Showy Goldeneye, Yarrow, Sulphur Buckwheat, Fleabane, and Goldenrod provide essential habitat to pollinators through late summer. However, there is another plant that provides essential food for pollinators that often gets a bad reputation, Wavyleaf Thistle.
Anyone who has dealt with invasive plants at their home, neighborhood, local park, trail, or their local nature preserve may have strong feelings about thistle. Invasive thistles are detrimental to biodiversity, destructive to habitat, and difficult to eliminate. Swaner Preserve has six types of thistles, four invasive thistles and two native thistles. Noxious thistles found on the Preserve include Canada thistle, Musk Thistle, Scotch Thistle, and Bull Thistle. Our two native thistles are Wavyleaf Thistle, primarily in sagebrush steppe habitat on the northern section of the preserve, and Elk Thistle, spotted in the wetland habitat on the southern section of the preserve. Every summer, our team sees native Wavyleaf Thistle that has been trampled, pulled, or cut along the Stealth, Blackhawk, and Glenwild trails. We know that these thistles aren’t removed with malicious intent and love when folks get involved to help remove invasive weeds, but we want to protect native plants in the process!
Wavyleaf Thistle or Gray Thistle (Cirsium undulatum) is gray-green due to the hairs covering the plant, it grows 2-5 ft in height and has wavy, lobed leaves with spines on the end. The flowerheads are urn-shaped with light pink to white blooms. The plant provides essential food and habitat to pollinators in the late summer though fall, when wildflowers become less abundant. It also provides food and nesting materials for birds. Wavyleaf thistle adds beauty and biodiversity to the landscape, without outcompeting other native plants. Next time you see a native thistle, appreciate its beauty, say hi to any bees that may be visiting, and leave it how you found it: in the ground. If you aren’t confident in thistle identification yet, follow one simple rule: if it’s the color of sagebrush (grayish blue/green), “leave” it be! Not sure? Check out our native vs. invasive thistle guide or reach out to Swaner for identification help!
Wavyleaf Thistle
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