These are growing in my garden in Ashby at the moment, although they have a more distinctively purplish tinge in real life than in these photos! Growing near rhubarb crowns...and the largest about 12cm in diameter, and there are several clumps of them. I'm wondering if the purplish/violet colour might indicate that they could be wood blewits, but the pictures on Naturespot don't show them growing so close together or with the caps upturned like this, although that could be an age/ontogeny related feature of course, I suppose. Any pointers gratefully received!
They look quite like wood blewits to me- the caps will wave about a bit especially with rapid and crowded growth. Have you been feeding the rhubarb generously? they like to grow on fertile soil such as places in a garden which have been mulched with garden compost or leafmould. I manged to cultivate them in a garden I worked at in Stoneygate some years ago, by placing elderly (past eating stage!) blewit caps gill-side down on piles of mixed beech leaves and grass clippings. Successful fruiting started within 18 months.
Thanks for the info, Sally, most intriguing! The rhubarb has been left to its own devices for years, but I made a raised bed round it this summer and added some compost...maybe that's what brought them on? Do I take it you grew them to eat then?