Last year on Shapwick Heath NNR in the Somerset Levels, there were masses of marsh thistles and lots of bumblebees feeding on them. One meadow, for example, with five ditches across it had 200+ bumblebees on several occasions (that was counting one side of each ditch). This year that meadow has practically no marsh thistles and these are rather small. Elsewhere on the site, there are either very few or no marsh thistles.
The meadows were pretty soggy most of last summer. However, some did dry out enough to cut but others were too waterlogged and only dried out about March this year. Some areas are just tussocky patches that never get cut. However, all these areas are either devoid or marsh thistles or only have a few and stunted ones at that.
Away from this site, I am finding some normal sized marsh thistles, but not in any great numbers down on the Levels, but up in clearings in woods on the hills there are lots (with masses of cuckoo bumblebee drones).
I wonder what’s happened - did the seeds rot in the ground? or was it the horrible spring? Has anyone else noticed a lack of marsh thistles?
The levels would have been so waterlogged at the end of the summer that the seedlings probably struggled to germinate. The seeds normally germinate in autumn or spring, so the prolonged cold spring could have added to the problem. Also, the seedlings need bare patches of soil and access to light, and they do not tolerate competition from grasses and other vegetation well. So, if some areas were not able to be cut and cleared due to the weather then this would also be an issue. I guess it was not so waterlogged up in the higher locations, so the thistles have faired better in these areas. I am hoping to visit Shapwick Heath NNR soon, so can discuss this with the site manager. Thanks