Sunday, 20 November 2016

A thatch moss

A family visit to St Fagans today left the bryologist in me frustrated at the inaccessiblity of the mossy thatch which covers many of the buildings. Even the eves were out of arm's reach, but beneath one building I was lucky enough to find a small fragment of rotten thatch that had fallen from the roof above.

Much to my surprise, this was covered in what I think has to be Bryum moravicum (with just a little B. argenteum for company). Branched, filamentous, slightly papillose brown gemmae were abundant in the lower and mid leaf axils.

B. moravicum isn't mentioned as occurring on thatch in any of my books, though known substrates include rotten wood as well as living bark. My (incomplete) copy of the VC41 database doesn't list any records since 1993, but I'll await Barry's confirmation of its current Glamorgan status.

Update - a few more photos added below. Gemmae were present on several of the shoots, but by no means all of them.


  1. Very interesting George. I've never seen 'Flabby Thread-moss', so am not qualified to comment on your I'D, records show that Roy recorded on three occasions; 1988 Coed Coesau Whips ST197857, and in 1993 at Llanbethery ST06J and Edmondstown ST09A

  2. PS it sounds like obtaining permission to take a proper look at the thatch could be profitable

  3. Thanks Barry...those are the only records I have on my system.

    Hopefully Sam can comment on the ID. I can't see what else it can be (surely too small for B. pseudotriquetrum, and without any hint of red on the leaves).

    I have a feeling Sam mentioned having looked at the thatch at St Fagans in the past...

  4. Richard Lansdown and I spent a day doing the St Fagans thatch a couple of years ago with permission and using a ladder. We also did a couple of Vale thatches that day.

    George's moss does look like Bryum moravicum. This species has declined dramatically in south Wales as far as I can see. I saw it several times in VC35 in the early 2000s but not recently.