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A Sinister Common Purple Wildflower for Ohio’s Summer.

July 17, 2011

Canada Thistle

This plant is pervasive along roadsides and in waste areas- you’ll often see them in colonies of multiple plants.  It started blooming in central Ohio in late May, and it’ll continue through the summer into early autumn.  It’s the most common thistle by a wide margin in this area.

It has multiple light purple blooms.

The flower head is small and compact, and not unattractive.

The leaves tend to be spiny and wavy, particularly on the lower stalk.  But this can vary among different populations.

Here in mid-summer, many of these plants have fuzzy seed heads replacing the flowers.  Each flower head can produce 40 to 80 seeds.

This is a very hardy plant…and now I’ll get to the sinister part of this blog title.  Unfortunately, Canada Thistle is an invasive species from Eurasia.  It most likely came to North America as a passenger in contaminated hay and grain seed in the 17th century.  It is hard to eradicate due to its deep roots that can keep it going for multiple years- cutting it down will not get rid of it.  Luckily this plant does best in waste type areas, and it is not without some benefit- some birds and insects feed upon them voraciously.

The bottom line with Canada Thistle is that very few people will say anything good about it- it is considered to be a weed even in its native range- it doesn’t get much lower than that, botanically speaking.  Googling this plant will bring up many pages on how to eradicate it, and I’ve seen it being controlled (presumably with herbicide) in the Metro Park system so that it doesn’t crowd out native plants.  But it looks like it will be around a while, and I bet birds such as finches would put in a good word for it.

A final note on the name- Canada is unfairly associated with the name of this plant that is probably a native of the Mediterranean and southeastern Europe.  It is also known as California Thistle- I bet California resents that- Prickly Thistle, and even Cursed Thistle (how’s that for a name?).    Multiple common names for any one species is one reason that Latin names for plant species are popular, which is a good idea but I don’t want to get too academic on this blog, so don’t worry 🙂

9 Comments leave one →
  1. July 17, 2011 8:36 pm

    I recently included this thistle in one of my blog posts. It was interesting learning about its history, especially in terms of the laws passed (as early as the 1700s) requiring farmers to mow or do what they could to eradicate it. Even Ohio passed a law (in 1844).

    The seeds are floating everywhere here lately.

    • July 24, 2011 11:40 am

      You know you’re not winning any plant popularity contests when laws are passed against you!

  2. July 18, 2011 9:18 am

    Wonderful post about a (in a whisper) hated plant…it certainly is not ugly, like most everything God created, there is a beauty there…but I do remember Judie’s (my beloved wife) uncle and cousin, farmers from Illinois, stopping to visit us in Minnesota…we had, like we do now…bird feeders in the back yard…among them, a thistle seed feeder…they were irate about us propagating the thistle plant all over…they explained, they were in a life-long battle with the plant in their fields back home and couldn’t understand why people have to use it…I understood and understand but Oh those house finches, gold finches and others might be upset if we took it down…

  3. July 19, 2011 4:04 am

    From a far, this plant is not as good looking but your photos showed all of us how beautiful it can be. thank you for making us appreciate this plant with it’s pinkish flowers.

  4. July 19, 2011 5:31 pm

    Thanks for leaving a comment on my blog. I learned a lot from your thistle blog..but I would like to calm the fears of those who feed birds “thistle” seed. It is actually nyjer seed, and the plant is unrelated to the thistle.

  5. July 21, 2011 1:39 pm

    Well, being Canadian we don’t like it named after us! lol. We have a bit in our pasture and our donkeys LOVE it as does the llama. So it never gets to flower thankfully. Beautiful shots. I love the close up the best. I love purple and it is such a wonderful shape. Thank you for the lesson!!

  6. July 24, 2011 11:42 am

    Thanks for the comments everyone!

  7. August 17, 2011 8:04 am

    You made the ordinary look poetic 🙂 Added you to my favourite list.

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