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Ophioglossum vulgatum

southern adder's-tongue

Ophioglossaceae

Europe, temperate Asia, North America

Native to North America

SunFull Sun – Part Shade

WaterMedium

HardinessZones 4–8

Overview

Ophioglossum vulgatum is a small fern of old grassland, standing just 2-8 inches (5-20 cm) tall and easily missed among grasses. Unlike most ferns it does not form a leafy frond divided into many leaflets; instead each plant raises a single undivided, oval to lance-shaped sterile blade 1-4 inches (2.5-10 cm) long, smooth and pale green, from which a slender fertile spike emerges. This spike, the adder's tongue of the common name, carries two rows of fused sporangia along its tip and releases spores in summer. The fern grows from a short fleshy underground rhizome and spreads slowly by root buds into loose colonies. It appears in late spring, stands through summer, and dies down by autumn. It grows in damp, unimproved grassland, old meadows, dune slacks, and grassy banks on neutral to base-rich soils, and depends on a fungal partner in its roots. It is slow to establish and intolerant of ploughing, fertilizer, and heavy grazing, so it has become scarce as old grassland has been lost. Its small size and single plain blade make it hard to spot until the spore spike appears.

Native Range

Ophioglossum vulgatum is native to Europe, temperate Asia, and North America, growing in damp, unimproved grassland, old hay meadows, dune slacks, and grassy banks. It favors neutral to base-rich soils that have escaped ploughing and heavy fertilizing.

Suggested Uses

Grown in wildflower meadows, damp lawns, and conservation grassland rather than borders, where it forms part of old-meadow plant communities. It suits naturalistic and restoration planting on unimproved soils. It is of interest in botanical and fern collections for its simple, single-bladed form.

How to Identify

Recognized by a single undivided, oval to lance-shaped pale green blade 1-4 inches (2.5-10 cm) long, with a slender fertile spike rising from its base in summer. The spike carries two rows of fused spore cases along its narrow tip. No other grassland fern of its range pairs a single plain blade with this tongue-like fertile spike, which makes a fertile plant easy to name even though sterile plants are cryptic.

Appearance

Size & Dimensions

Height2" - 8"

Width/Spread1" - 3"

Colors

Foliage Colors

green

Bloom Information

This fern does not flower. The fertile spike ripens in summer, usually June and July, releasing spores from two rows of fused sporangia before the plant dies down in autumn.

Detailed Descriptions

Foliage Description

Pale green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-8 hours of direct sunlight daily

• 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 Range6.0 - 8.0(Neutral)

357912

Soil Types

loam clay

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

several years to establish

Care & Maintenance

Care Guide

Grows in full sun to light shade in damp, unimproved, neutral to base-rich grassland that is neither ploughed nor heavily fed. It is hardy to USDA zone 4 and dies back to its rhizome in winter, reappearing in late spring. Steady soil moisture through spring and summer is needed, and the fern declines under fertilizer, drainage, or heavy grazing. It depends on a root fungus and so is slow and unreliable to establish from spores or division. Light grazing or an annual late-summer cut maintains the open grassland it needs, and it has few pests but is vulnerable to habitat change.

Pruning

No pruning is needed. The single blade and spike are left to die back naturally in autumn. In grassland it tolerates a late-summer cut once the spores have shed.

✓ Toxicity

Non-toxic