Pasture Thistle Cirsium discolor
Perhaps the most abundant of the native thistle species in the Midwest, a short lived perennial in wetter/mild regions and a biennial in the dryer regions of the midwest. Its a late season nectar source and is one that really deserves real recognition(both in ID and in it’s benefits). Lacking ribs and line spines along it’s stem in it’s cauline phase, this species is more friendly than the invasive look-a-likes. Our native thistles have a more open capitulum in comparison to invasives as well. The real treasure, and why we see these species lasting only a few years on average(rather blooming once) is because of the sheer amount of nectar it produces when compared to other members of Asteraceae and invasive thistles. In this species in particular resources are poured into this nectar production, and high protein pollen production, costing much and leading to an individual of this species’ demise. Although it’s not just beneficial for nectar, short lived species leave behind bare soil openings for new seeds to utilize, and old stalks are perfect for over wintering insects, usually solitary bees. As I’ve mentioned in previous posts, our native thistles can be easy to ID once you get to know them in the midwest, and even easier in arid regions where they are extremely evolved to the point of specializing endemism occurring and alien traits, with their only issues being peoples stigma against the invasives and climate change getting in their way. This species in known for it’s short stature, classic pinnate leaves(common in our common natives), leaf margins having spines but no spines along it’s midvein or stem(also common in natives), a velvet like white pubescent underside( also common in native species), and a white line(usually caused from pubescence) on the phyllaries( the fused bractoid scales of the involucre on a capitulum). This species differs from it’s close and also common relative C. altissima (altissima meaning tall) in height and the amount of flowers on a capitulescence (C. altissima has more capitulum on average). C. altissima will also not have lobed leaves unlike other native thistles.
Invasive thistles, most of them not even Cirsium spp., will have no pubescence on their underside as well as have spines through out it’s entire morphology. Although Bull thistle can be often confused for a native despite its aggressive spines due to occasionally having a slightly tomentosed abaxial surface instead of the fully pubescent abaxial surface our natives have. also the spines are noticeable on bull thistle for being annoying
Many a thistle species gain direct notes of animosity and hatred in the midwest, weather it be because of their ruderal nature, their spines, or their untamed appearance. With that said, its somewhat understandable for those who see thistle to disregard or even actively remove them. I used to do it to all thistle without even thinking when I was younger; but, that was before I understood the incredible ecological importance of our native thistles.
We do have plenty of good Cirsium spp. in the midwest, although most are becoming less common with time and some are even rare or imperiled in their historic range, have been removed from other close populations/extripated entirely because of the reputation the non natives have, and there for have reduced vigor in their habitats overall. Pitcher thistle, Cirsium pitcheri, for example, has been placed on the federally threatened list due to it’s habitat, sand barrens and sand prairies, decreasing in size each year and the disjunction between these populations widening. Erie county, Ohio has a few populations, Cook county, Illinois has some populations, Porter county, Indiana has a decent population, LaPorte County, Indiana as well, but perhaps the largest populations in the Midwest are in Michigan’s dune systems. Aside from habitat loss, weeding and overshading from both invasive and native species are real threats.
Hopefully, y’all can be native thistle advocates and spread the word about how cool and important our native thistles are. Or grow them in your native garden as a pink/white late season nectar source and over wintering unit.
If y’all want to learn more, Check out. xerces societies 2016 pdf. by clicking the bold letters.
Photographed at Adena Mound Prairie, Cincinnati, Ohio.
