It must be a good year for thistles. It seems that most everywhere I look there are thistles in bloom. They really can be quite attractive. But of course, thistles have a bad reputation, largely because they are prickly, and two of them are listed by the North Dakota Department of Agriculture as noxious weeds. Both species, however, are introduced (the Canada and musk thistle).
The term thistle is a general reference to three genera of the Asteraceae or daisy family (Circium, Carduus, and Onopordum) that have prickly leaves and purple flowers. Perennial sowthistle (Sonchus arvensis) and Russian thistle (Salsola iberica) are not really thistles because they belong to different genera and in the case of Russian thistle even a different plant family (Chenopodiaceae or goosefoot family).
There are about a half dozen thistle species native to North Dakota, and they are not weeds. In fact, they are important sources of nectar and food for a variety of butterflies and other insects. Plus, as most birders know, their seeds are important food sources for many songbirds, particularly goldfinches.
Thistles are also important to humans. As you might expect because the thistle flowers can be quite showy, they are occasionally planted in flower gardens, particularly in Europe. The thistle is even the national emblem of Scotland.
As some of you know, Canada thistle has surpassed leafy spurge in acres invaded in North Dakota. So it is now our number one noxious weed. But do not blame the Canadians. Canada thistle is not native to Canada. I haven’t heard how it came to be called Canada thistle, but the plant is native to southeastern Europe and areas around the Mediterranean Sea. It was likely introduced to North America back in the 1600’s.
Perhaps like me, you may have noticed the flower heads of some of our native thistles in pastures have been eaten by some grazing animal, assumedly cattle or deer. But it could also be Eeyore. Some of you may recall that thistles are the favorite food of Eeyore, the donkey in the Winnie-the-Pooh stories.