The mystery of Adder’s-tongue (Ophioglossum vulgatum) in Bishop Auckland PATRICIA GRAHAM & DAVID SHIMWELL
Ophioglossum vulgatum (Adder’s-tongue) in a garden lawn in Bishop Auckland, 26 June 2020. Photographs by Sidonie Cumberland.
Introduction
There are a number of written assessments of the national and local distribution patterns of the seemingly uncommon fern, Adder’s-tongue (Ophioglossum vulgatum L.). The Online Atlas of the British and Irish Flora (BSBI/BRC 2020) considers it to be ‘an inconspicuous species which is very much better recorded than in the 1962 Atlas;’ and notes that ‘it has been lost from many lowland sites where the intensification of agriculture, grazing and drainage have contributed to its decline.’ The Wildlife Trusts website (2019) describe it thus: ‘an indicator of ancient meadows, it can be found mainly in southern England’ with a ‘localised distribution, and not very common.’ For northern England the opinions of two eminent botanists provide a sound overall view. In The Flora & Vegetation of County Durham, Graham (1988) wrote that it was ‘rarer than it used to be and now very thinly distributed, though easily overlooked and probably under-recorded.’ In the Flora of Cumbria, Halliday (1997) noted ‘an uncommon fern of short, damp, ‘unimproved’ grassland and woodland rides… easily overlooked and is capricious in its occurrence.’ This apparent caprice has made surveys of its changing distribution patterns a difficult task and the results may be dismissed as being ‘data deficient.’ For example, in the national survey, Change in the British Flora 1987–2004 (Braithwaite et al., 2006) it was recorded in only 15 tetrads which generated 42 observations (19 gains, 17 losses and 6 re-finds).
In the spring of 2017, we were given the opportunity to observe this caprice when a small population of Ophioglossum vulgatum was recorded on a lawn of a house in a low-lying neighbourhood of Bishop Auckland (v.c. 66), at an altitude of 94 m, some 30 m distant from the River Gaunless. This was its first sighting in this locality, in monad NZ2129, in a period of observation dating back to 1980. Personal observations suggested that from 1989 to spring 2017, the lawn had always been mown regularly and managed by the application of a proprietary brand of combined lawn feed, weed and moss-killer. Thereafter, the mowing regime and chemical applications became less frequent and the Adder’s-tongue was first noticed in 2017 when twenty plants – three fertile spikes – were counted. It has appeared each year since, the precise area of the lawn where it had occurred was left unmown in 2018– 2020 (see photograph on next page) and has witnessed an increase in area with thirty plants and four fruiting sporophytes early in 2020. Some ten vegetative fronds beyond the shade of a tree canopy desiccated and shrivelled in the dry spell of weather in May 2020 and could not be found by mid-summer.
The plant community
The lawn sward is dominated by eight relatively fine-leaved grasses: Anthoxanthum odoratum (Sweet Vernal-grass), Cynosurus cristatus (Crested Dog’s-tail), Festuca rubra (Red Fescue), Holcus lanatus (YorkshireBSBI NEWS 146 | January 2021
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