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I'm trying to identify a prickly, burr-type plant growing wild in my yard in Massachusetts, USA. I found about five of them in an area of full sun. Temperatures over the last few months have varied between 70°F and 100°F. The ground is regular garden soil, and these plants are sharing space with pokeweed; lamb's ears; goldenrod; and some other wild things, the names of which I don't know.

Description:

  • They're about three feet tall, and are covered with round orb-shaped things which I'll call burrs until I know if that's the correct term. The entire plant is covered with thorns, including the leaves and the stalk. The stalk also has white fur.
  • The burrs are at the junctions of leaves and stalk, similar to perennial plants, as opposed to some wildflowers which are single stalks with flowers at the top.
  • The burrs grow to a certain size, which is different with each one, from a radius of anywhere from one to three inches, at which time another section pushes through the top, which I'll call the second stage.
  • The second stage appears to be a flower, but only opens a small amount and doesn't have petals, just spikes. They vary in size, shape and color, even on the same plant. For example, my pictures show a plant that has both dark and bright purple second stages.
  • At some point, the burr attached to the stalk becomes brown and opens to reveal narrow long things which I assume are seeds. These are soft and furry, and easy to separate and remove.
  • The plant has a continuing life-cycle, with young burrs still appearing after others have died off.

My questions:

  • What is the name of this plant?

  • What is the second stage, and why does it vary so widely even on the same plant?

  • Since only the original burr goes to seed, while still attached to the stalk, where does the second stage go? It would make sense that it would fall off, but I can't find any on the ground.

The first picture has a good view of three different stages on the same plant. Below that are close-ups of each section from that plant. I've also included a picture of a different plant which shows the original burr with the second stage just pushing through; and a third which shows new growth and a large old brown seed pod.

Click on the pictures for closer view.

Whole plant with different stages close-up or dark purple part Bright purple part Section after seeding View of different size orbs getting ready for next phase Large seedpod with new young orbs

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    Its not as complicated as you think - the bulbous 'burr' a the bottom is the ovary of the plant and part of the flower - that's where the seeds will form - the 'petals' or the coloured tuft at the top are what attracts insects for pollination/fertilisation - once fertilized, the 'petals' die back and the bulbous burr at the base becomes rounder (you can see that in your pics). Over time, the seeds ripen and the 'burr' dries out and opens to reveal the seeds. Any 'burrs' which retain the original oval shape probably do not contain fertile seeds because they weren't fertilized via pollination.
    – Bamboo
    Sep 11, 2016 at 11:14
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    I should have done this as an answer, couldn't fit it all in one comment - despite its different appearance, cirsium flowers work in the same way as other flowers, they just look a bit different. The different colours of the petals merely reflect the age and stage of development of each flower; its not in the least unusual to have buds, newly opened flowers, and flowers dying back and/or going to seed on any plant, if you think about it.
    – Bamboo
    Sep 11, 2016 at 11:19
  • Bamboo you really should just make these comments into an answer. I am a bit confused by the infertile seed gig. Why wouldn't they have been fertilized?
    – stormy
    Sep 12, 2016 at 19:11
  • Some or most thistles are biennials. That means it takes two years, two seasons to get to the flowering or reproductive stage. The best way I've found is just pull these guys up when you find them, best done the first season as a basal rosette but before flowering the second year.co.stevens.wa.us/weedboard/htm_weed/thistle_comparison.htm
    – stormy
    Sep 12, 2016 at 19:25

2 Answers 2

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Some or most thistles are biennials. That means it takes two years, two seasons to get to the flowering or reproductive stage. The best way I've found is just pull these guys up when you find them, best done the first season as a basal rosette but before flowering the second year.http://www.co.stevens.wa.us/weedboard/htm_weed/thistle_comparison.htm I think this is good ole 'Bull Thistle'. Your question and pictures are excellent, Sue. The area you are discussing with the poke weed and this thistle sounds like a wonderful 'wild' food grouping. Solidago I have in my greenhouse!This helps attract pollinators for the end of the season. I've got wild flowers, thyme that attract pollinators for the beginning and middle of the season. Did you make this grouping on purpose? Kudos! You must love artichokes, yes? I tried growing them as a perennial here, not happening.

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  • I didn't make the grouping on purpose. I don't have that kind of talent! I have some other things that aren't visible in the picture and the bees are very happy over there. I love watching them. There are a few earwigs on the burrs, but they're not moving. I guess they're either dormant or have been prickled to death! There's a lot of wild Solidago around my yard, but my hubby's allergic when they're in bloom, so I have to pull them and put them way back in the woods where the bees can at least feed until the flowers die. Yup, I do love artichokes!
    – Sue Saddest Farewell TGO GL
    Sep 14, 2016 at 21:04
  • I used solidago as a super filler when I was playing 'florist'! Has your hubby tried any nasal steroidal sprays? These are not over the counter. Need to be prescribed. I am the top of the worst of hay fever people. No matter, I hayed for most of my young teenage life. Loading and unloading bales of alfalfa and orchard grasses. Dust and pollen galore. 'Nasacort' or its generic works miracles. Like no allergy whatsoever. I rode Harley's through the hay lands being harvested and no problemo. Now I don't even have to use those sprays at all. How about a vase of flowers outdoors?
    – stormy
    Sep 14, 2016 at 21:11
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I think this could be a common thistle, judging by the purple flower and spikes. The Wikipedia article on it: https://en.wikipedia.org/wiki/Cirsium

I don't know the answer to the last two questions though.

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