I'm attaching pictures of a thistle I came across recently on the banks of a steam in the Yorkshire Dales. It was next to stands of Cirsium arvense and Cirsium palustre. The plants seemed to show characteristics of both the above and I'm wondering if they were hybrids? Thus they were similar to C. arvense, but with larger flowers, more red and less green in the foliage, lankier habit. Also the arvense were not flowering here as the palustre are earlier flowering. Compared to local palustre they lack the spiny stem, are greener and have paler flowers. Any help with the id would be appreciated.
all my instincts are saying these are Cirsium arvense. From what I can see from your pictures the stems do not have the spiny winged stems associated with C. palustre, and the scales on the outside of the flower heads are not spiny, the lack of these two characters also rules out Carduus crispus.
As for it being a hybrid, well that is impossible to prove either way from your photographs unfortunately but usually you would be looking for plants which were intermediate between the two suspected parents. Bearing in mind that hybrid offspring frequently back-cross to one parent and so the balance of characters expressed becomes biased towards that parent in subsequent generations, it is very difficult to determine definitively a lot of the time. Close examination of all the plants features in the field is the key...
Having consulted Stace there is a hybrid known between C. arvense and C. palustre.
He says, (and I quote) -
Should you return to the site have a close look at the stems of the different species of Cirsium there to see if the plants you are interested in share any characters. If they do please do let me know!
I hope that helps somewhat...!
Thanks for that. I have heard of C. celakovskianum, but have not seen a detailed description and there are only two records from our vice-county. That is one reason I asked. I do suspect these are a hybrid. It is hard to show in the photograph, but the deifferences were very obvious in the field as these plants were immediadely adjacent to extensive stands of both arvense and palustre (both of which I'm very familiar with). These plants really stood out as distinctly different and seemed to be intermediate in superficial characteristics. I'll give them another look if I'm back in the area and see if I can get some better pictures. These were the only 2 I had as I really didn't think about it much at the time.
Thanks again for your help.
That is brilliant :-) If the hybrid is known for your vice-county and you observed intermediate characters it certainly sounds like there is a very strong chance that your specimens are C. celakovskianum. It might be worth informing the vice-county recorder too.
Apologies if my initial post was at all patronising.