Ophioglossum vulgatum (southern adder's-tongue)

Ophioglossum spp.

Adder's-tongue fern

Ophioglossaceae

Cosmopolitan, on every continent except Antarctica

Native to North America

SunFull Sun – Part Shade

WaterMedium

HardinessZones 4–9

Overview

Ophioglossum spp. is a genus of small, primitive ferns in the family Ophioglossaceae, known as adder's-tongue ferns and found on every continent except Antarctica. The genus holds around 25 to 30 species. Unlike typical ferns, each plant usually produces a single, fleshy, undivided sterile blade, oval to lance-shaped and 2-15 cm (0.8-6 in) long, paired with an erect fertile spike that bears two rows of sunken sporangia and gives the genus its common name. Plants are 5-30 cm (2-12 in) tall overall and grow from short rhizomes with fleshy roots. The genus is noted for very high chromosome counts, with some species exceeding 1,000 chromosomes. Adder's-tongue ferns depend on mycorrhizal fungi throughout their lives, which makes them very hard to cultivate and slow to appear, sometimes remaining dormant underground for a season. They grow in damp grassland, meadows, dune slacks, and open woodland, are easily overlooked among grass, and have declined in many areas with the loss of old, unimproved grassland.

Native Range

Ophioglossum spp. is nearly cosmopolitan, growing on every continent except Antarctica. Species occur in damp grassland, meadows, marshes, dune slacks, and open woodland across temperate and tropical regions.

Suggested Uses

Ophioglossum spp. is of interest in botany and grassland conservation rather than in gardens, where it is regarded as an indicator of old, species-rich meadows. It is seldom grown deliberately because of its dependence on soil fungi.

How to Identify

Each plant typically has a single fleshy, undivided oval to lance-shaped sterile blade 2-15 cm (0.8-6 in) long, with an erect fertile spike rising from its base that carries two rows of sunken sporangia. Overall height is 5-30 cm (2-12 in). The undivided blade and the tongue-like fertile spike set adder's-tongue ferns apart from other ferns.

Appearance

Size & Dimensions

Height2" - 1'

Width/Spread2" - 6"

Colors

Foliage Colors

green

Bloom Information

Ophioglossum spp., as a fern, does not flower. The fertile spike releases spores from two rows of sunken sporangia, mostly in late spring and summer, after which the above-ground parts often wither until the next season.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.0 - 7.5(Neutral)

357912

Soil Types

loam sand chalk

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Ophioglossum spp. is rarely cultivated because it depends on mycorrhizal fungi and seldom survives disturbance. In the wild, species grow in damp, low-nutrient grassland and meadows in full sun to light shade, in moist soils of varying pH from acidic dune sand to neutral or slightly chalky loam. Constant low fertility and undisturbed ground favour the fungal partnership the fern needs, while fertiliser, ploughing, and drainage cause populations to disappear. Plants may stay dormant below ground in dry years and reappear later. Where present, they are maintained by traditional hay-meadow or grazing management rather than by garden care.

Pruning

No pruning applies. The small fronds and fertile spike are left undisturbed; mowing or cutting before the spores ripen in summer reduces reproduction, so where the fern is valued, grassland is cut late in the season.