Tortula truncata – Common Pottia

As of October 2022 we had only listed two species of Bryophytes (mosses) in the Garden on account of the difficulty in identifying them to species level.

We recently viewed the moss below growing on the wetland soil substrate and realised it was likely a different species to the ones already recorded. Having recently attended a Bryophyte survey day on the Mendip Hills, we had already invested in a copy of the brilliant field guide: Mosses and Liverworts of Britain and Ireland a field guide – British Bryological Society (ref 14: Click HERE).

Like many guides, this one starts with some introductory information followed by a key to species. With the remainder of the book consisting of species accounts. The first step was identifying if our moss was an Acrocarp or a Pleurocarp, which in reality means if the spore capsule stem (seta) emanates from the end of the stem or from the middle of the main stem.

Using a microscope on a small sample, although this would probably be doable by eye and certainly using a hand lens, we could clearly see the stem and capsules originated from the tip/end of the stem.

Having therefore determined our specimen to be a Acrocarp, the user of the guide is then presented with groups of mosses with a descriptive title and an accompanying set of line drawings to help direct you towards the species accounts you need to consider.

We settled on the group ‘Acrocarps with leaves that have a translucent blade’, which under the microscope we could see ours clearly had. Indeed the line sketch provided for this group actually used, as an example, the very species (Tortula truncata) that we would eventually determine our species to be.

We turned to the species account and with a little comparing to similar named species we were left convinced we were looking at T.truncata. Further diagnostics were that the shoots were 3-5mm (which ours were, similar species could have much larger shoots), leaves widest above the middle (see above photograph) and a capsule not much longer that wide (you don’t count the pixie hat type structure, the lid), which can be seen to be the case below…


We compared to all the named similar species in the guide and nothing else really fit, and with the books photographs and diagrams included with the species account, and the fact this is one of the most frequent and common species out there, we are relatively satisfied we have the correct species.

Overall we found the guide easy to use. Having seen it used by experts in the field we are confident this is the best tool for the job. We are also finally glad to add one more moss to our far to short a list of lower plants (sadly still no liverworts recorded in the garden).

DC: 22.10.2022