Wiltshire and Swindon Biological Records Centre

Adder’s-tongue Fern - Ophioglossum vulgatum

It was named after a belief that its similarity to a snake’s tongue meant it could be used as an antidote to snakebite.

Adders Tongue, WSBRC/Sharon Pilkington


This is a native small fern of damp grassland which is regarded as an indicator species of unimproved neutral grassland. It is most frequently found around the Braydon Forest area in the North of Wiltshire, for example at Clattinger Farm. Salisbury Plain military training estate, other chalk downland and damp woodland sites in Wiltshire are other habitats known to support Adder’s-tongue fern. It prefers old pastures that have not been ploughed.


It is an unusual fern because the fronds do not uncurl as they grow. It has one single short frond that grows each year by pushing through the ground in March or April; it can reach 30cm but seldom appears as long as this as half of this structure is often buried. The frond divides to form a sterile oval leaf (1-12cm long) that is a dark green colour and encases a tongue-like spore-bearing spike. Mature plants have an upright spike reaching higher than the sterile blade; the spores are ripe from May to August. It often occurs as either solitary plants or small populations making it hard to spot, especially when it grows among long grass and herbage.


Over the years suitable habitats have been declining due to the intensification of agriculture; grazing, drainage and neglect have contributed to its decline. Any management that alters the moisture content of the soil will have an effect on Adder’s-tongue populations.


Being protected generally under the Wildlife & Countryside Act 1981 it is an offence to uproot Adder’s-tongue without the landowner’s permission.