Plant of the Week: Old Field Thistle
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Written by: Engineering Conservation Crew
Why would someone write an appreciative blog about thistles? Aren’t they all just terrible? Well, Wisconsin has a handful of native thistle species, including our plant of the week, Old Field thistle or Cirsium discolor. Here are some of its benefits…As the name suggests, field thistle prefers open patches of land like prairies, forest edges, and roadsides. Field thistle can help promote recovery on disturbed grazing land by spread through overgrazed areas, creating a natural border that deters wild grazing species. Whereas invasive thistles tend to take over and create monocultures, native thistles play nice with other species and allow for higher biodiversity.Native Wisconsin thistles are a tad less spiky than most of their weedy cousins, such as bull thistle or Canada thistle, appearing more hairy than spiny from a distance. A fun, yet risky, way to determine if a thistle is native is to “pet” the plant upwards with your hand. A native thistle will not prick you as its barbs only face upwards! If you think this sounds like a horrible idea, another way to distinguish native thistles are the pale white underside of the leaves. This feature is unique to native thistles and nods to the scientific name, Cirsium “discolor.”
Some wildlife are specialized to seek out this species. Goldfinches are particularly fond of field thistle seed. Furthermore, each field thistle flower head is made up of more than 100 tiny flowers, allowing it to produce abundant nectar for hummingbirds. Butterflies, like the painted lady, will seek out this plant during their larval stages to feast on.
We hope you hate the idea of thistles as a whole a little less now. Field thistle is abundant at the UW Arboretum prairies if you’re looking to test your new knowledge. Our team was excited to see a few of these individuals at High Point Confluence Pond this week.
Each week during the growing season, the Engineering Division focuses in on a Plant of the Week to raise awareness of different plants in the field that benefit our environment. The Engineering crews in the field tasked with conservation share expert insight on these plants and their benefits each week in a creative way!
