Ophioglossum vulgatum aka Adder's Tongue

Ophioglossum vulgatum has the common name adder's tongue fern. It is part of the fern family Ophioglossaceae. Other names are adder's grass and snake's tongue fern. Its native range spans Europe, Britain, and North Africa. It reaches into northern and western Asia as well. The RHS confirms its native status in Britain and Ireland. In the wild, this fern grows in damp grassland. It also grows in fens and patches of scrub.

This small fern grows about 1 foot [0.3 metres] tall. Its fronds rise straight when they first come up. Most ferns unfurl from curled croziers, but this one does not. You can divide the plant through its rhizomes, or underground stems. Take care when doing so, as the roots break easily. PFAF lists May to August as the time its spores ripen. Its notes on raising new plants refer to spores, not seeds. The sources give no more details about its spore-bearing parts.

Choose an open site with moist soil that drains well. PFAF states that this fern cannot grow in shade. It grows in sand, loam, and clay soils. Soil can be mildly acid, neutral, or mildly alkaline. PFAF lists USDA zones 4–8 and cold tolerance near −15°C. A meadow or garden border can suit this fern. A sunny edge of woodland is another suggested site. Once plants take hold, leave them in place. Do not move them around.

It can be hard to get this fern to take hold. At its young, spore-grown stage, it works with mycorrhizal fungi. Sow ripe spores on top of sterile soil rich in humus. Keep this soil moist while the plants are young. They need humid air as they take hold, too. PFAF says to wait at least two years before planting them outdoors. These needs mean raising new plants takes time and care. The evidence names no pests or diseases specific to this species.

PFAF lists the leaves as a vegetable but gives few details. It reports no known cases of poisoning from this species. This does not prove that the fern is safe to eat. PFAF urges care, since some ferns contain substances that cause harm. Past records describe using roots and leaves on wounds and skin ulcers. They also note mixtures meant to help stop bleeding. These past uses do not prove safety or health benefits. PFAF lists no other uses. It flags no risk of this fern becoming a weed.