Identification notes
One of a class of small pioneering acrocarps with a short life-cycle, P. acuminatum is normally seen with capsules, which make it conspicuous. It’s a common enough species of disturbed, well-drained acid soils and typically grows in dense patches of shoots.
Its capsules usually mature in spring or summer, so in the winter you may come across immature plants without them. These are confusing as they can be mistaken for other acrocarps with long, slightly curved leaves, such as Dicranella heteromalla, Ditrichum heteromallum or even Flexitrichum gracile. Field characters that will point towards Pleuridium acuminatum are perichaetial leaves at the top of the shoots much longer than the uppermost stem leaves, surrounding a small structure which will contain either antheridia or archegonia (but not both – P. acuminatum is dioicous).
If capsules are present, then it is usually a straightforward species to recognise. P. subulatum is less common but more likely on neutral to slightly acidic soils. A dissecting microscope is often needed to check for bud-like male branches in the axils of the stem leaves in that (monoicous) species; some gentle cleaning may also be needed to remove soil and detritus. Pseudephemerum nitidum grows in similar places, but its perichaetial leaves are about the same length as its upper stem leaves.
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