No, I haven't grown it.
Here's a possible source, though.

Russell Graham, Purveyor of Plants
Mailing Address:
4030 Eagle Crest Road NW
Salem, Oregon 97304-9787 (United States)
Phone: 503-362-1135

You can go to the watchdog and look up this company, which is where I originally found the information. The first rating is where your plant is mentioned.

Thanks for the tip. I had done that already and emailed him but have not received a response. So the search continues....

Any other ideas out there?

Ah, I remember that plant! A friend gave me some years ago and it promptly took over the garden. I then weeded it aggressively and haven't seen it since. But I sent a note to the friend to see if she still had it kicking around in her yard. Send me a note if I don't respond.

Hmmm. How did it take over the garden? The plant I am talking about does not set seed. It is supposed to be clump-forming and not spread. Can you describe how your plant spread? The single form is ordinary meadow buttercups and they do self-seed prolifically.

I am interested to see that you are in Minnesota. I keep running into a Minnesota connection with people who know this plant, altho it is European. Wonder why that is?

Well, let's see. I had this plant more than 20 years ago, but if I recall correctly, it spread from stolons, or runners, rather like a strawberry. That spot in the garden was rather clayey, so it may have found it very hospitable. The flowers on the plant I had were definitely not single; in fact, they looked exactly like the photos in the link below. Is that what you're looking for?

The woman I got it from had made a number of trips to England, if that helps with your mystery at all.

Here is a link that might be useful: Photo just like the plant I had

It does look like the plant--in Central Park, no less!--but I have only seen photos so can't be 100% certain. The different behavior reports are confusing. It is possible that there are different clones out there.

The behavior could simply be a matter of conditions (or reporting). The friend replied that she still has one of the plants crop up in her yard now and then despite her efforts to eradicate it. So I don't have easy, sure access to the plant, but perhaps I'll ask her to save the next one she finds. That would probably be next year, but if you don't locate it before then, feel free to check back with me. Good luck!

Thanks a lot. I'll keep your kind offer in mind if I don't find it first.

Ginny, did you ever find your buttercups? The friend who provided the plant to me originally has given me a new sample, which is happily spreading in the pot provided.

I found this post when trying to look for what we'd determined is the precise name of grandma's "sailor's buttons" -- yep, I think I'm the one who started Ginny on this quest years ago -- so I had to resurrect the thread with a photo of the specific plant we were discussing.

This variety definitely does NOT reseed or spread via runners, as do many ranunculae (?). It's a clump that has expanded very politely ever since I was able to locate it in a spot where it's happy. This location is reliably moist - even has standing water briefly during hard rains - and reasonably sunny.

Apologies for the graininess of the photo; it's a portion of a larger picture, where something else entirely was the focus. But I had to show Ginny, and thank her again for helping me ID this fabulous plant!

Thanks for this wonderful photo, Deeje, and for resurrecting this thread. A beautiful old perennial in New England gardens--but I have never knowingly seen it "in person". I've probably seen it and just not known it. Haven't looked for it in years and now I'm not really adding new plants.

Well, if you ever decide you have a spot, Ginny, thanks to you I could spare a division now!