Ornamental · Aspleniaceae
Hart's Tongue Fern
Asplenium scolopendrium
Give it deep shade, steady moisture, and a lime-rich soil, and this glossy strap-leaved fern holds evergreen color through winter.
Full shade
Every 5–10 days
USDA 5–9
12–18 in · 30–46 cm
Overview
What sets the hart's tongue fern apart is the entire fern shape it abandons. Its fronds do not dissect into the lacy, feathery outline associated with the group. They emerge instead as long, glossy, undivided straps of bright green, arising from a compact central crown and arranging themselves into a tidy shuttlecock of foliage.
As a member of the spleenwort family, it grows wild across Europe on shaded limestone walls, rocky banks, and cave mouths, and that ecology dictates its needs in cultivation. Reproduce it and you supply cool shade, a sweet alkaline soil, and steady moisture without waterlogging. In a suitable position the plant is evergreen, retaining its fronds through a hard winter.
Growth is slow and deliberate rather than quick, so this is a structural plant rather than a filler. Given shelter and shade, it contributes a bold, almost reptilian texture that reads well in a dark bed under trees or against a north wall.
Care
The short version: it performs best in full to partial shade, in soil kept evenly moist yet sharply drained, in a sweet alkaline mix carrying some lime, and under the higher humidity typical of the shaded rock it colonizes.
Light
This is a shade species, and it should be sited accordingly in full to partial shade, the dappled or deep cover it receives beneath trees or against a north wall. Direct sun scorches the fronds because a shade-adapted leaf transpires faster than it can compensate, so keep it clear of hot afternoon light.
Water
Maintain soil that is evenly moist but never waterlogged, watering every 5 to 10 days and more frequently during dry spells or the first season after planting. Drainage governs everything: the plant tolerates neither standing water nor drought, so a moist medium that drains sharply is the target.
Soil
Grow it in humus-rich, well-drained soil on the alkaline side, ideally a pH between 6.5 and 8.0. It is among the few ferns that genuinely favors lime, which is why a chalky or limestone-rich substrate suits it where acid-loving plants would fail.
Temperature
Its hardiness is considerable, enduring winter lows to -20°F (-29°C) and summer heat to about 75°F (24°C). That tolerance range is precisely what allows it to remain evergreen across zones 5 to 9 rather than retreating below ground.
Humidity
Adapted to shaded rock and cave mouths, it prefers moist air around 50% to 80%. In a dry interior or an exposed bed the frond tips brown as transpiration outpaces uptake, so group it with other plants or place it where the air stays still and moist.
Feeding
Ferns are light feeders, so restraint matters. A single application of diluted, balanced liquid fertilizer in spring suffices, and overfeeding is counterproductive rather than beneficial.
Pruning
Little intervention is required. Remove dead or damaged fronds as they occur, and cut back the tatty, winter-burned old fronds in late winter, timing the cut just before the new croziers unfurl.
Repotting
A containerized plant needs shifting only every 2 to 3 years, or sooner if roots emerge from the drainage holes, the crown becomes congested, or water passes straight through. Move it into a slightly larger pot with fresh, lime-rich, gritty medium.
Size & spacing
It is a compact, slow grower attaining roughly 12 to 18 inches (30 to 46 cm) in height and a comparable spread. Allow each plant 12 to 18 inches (30 to 46 cm) so the crowns can develop their full rosette of fronds.
When to plant
This is a hardy, unhurried fern. Sow ripe spores indoors in spring to raise your own stock, and plant young ferns out in spring once hard frost has passed. It remains evergreen in zones 5 through 9, so an established plant retains its fronds year-round rather than dying back to ground level.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Sow ripe spores indoors in spring at about 15°C (60°F)
- Plant: Spring, after the danger of hard frost has passed
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Most problems on this fern derive from water and light rather than pathogens or pests. Excess moisture at the roots and excess sun on the fronds account for nearly all of it. Match your symptom below, then correct the underlying condition before the damage advances.
Fronds collapsing above blackened, mushy roots
Waterlogged soil starves the roots of oxygen and invites root rot, which is the mechanism behind collapsing fronds here rather than an airborne disease. A lifted crown confirms it: affected roots turn soft, dark, and foul-smelling in place of firm pale tissue. Excise the rotted roots, restore sharp drainage, and repot into a gritty, lime-rich medium so the crown can recover.
Fix:
- Improve drainage immediately
- Reduce watering frequency
- Repot into a gritty, well-drained, lime-rich mix and trim away rotted roots
Scorched tips and margins across the fronds
A shade species exposed to direct sun loses moisture from the frond faster than the roots replace it, and the result is sun scorch at the tips and margins, made worse by dry air or a soil that dried out. The pattern is diagnostic: the sun-facing side browns while shaded fronds hold their green. Relocate it to deeper shade, raise the ambient humidity, and keep the soil evenly moist to halt the damage.
Fix:
- Move to a shadier spot
- Raise humidity around the plant
- Keep soil evenly moist
Old outer fronds browning and tattering after winter
Because the plant is evergreen, its oldest outer fronds stay exposed through winter, and cold combined with wind desiccation produces winter burn on that older tissue. The disorder is cosmetic: the central crown remains viable and flushes new growth in spring. Remove the tattered fronds in late winter, timing the cut just before the new croziers begin to unfurl.
Fix:
- Cut back damaged fronds in late winter before new croziers unfurl
Toxicity
For a shaded planting shared with pets and children, the verdict is favorable: this fern is safe. As a true fern it carries no known toxin, so cats, dogs, and grazing animals are not at risk near it. The one genuine caution is mechanical, since the fronds and spores can scratch or irritate sensitive skin, which is why washing the hands after handling is sensible.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
No toxin in this fern reaches cats, so it poses no poisoning risk to them. An exploratory bite may bring the mild digestive upset any fibrous plant can cause, and nothing beyond that.
Dogs None
The plant offers dogs no toxic compound to react to. A chewed frond might prompt some drooling or a short dip in appetite from the roughage, but the fern itself does no damage.
Horses None
Grazing beside it presents horses no hazard. A true fern of this group carries no toxin capable of affecting them.
Rabbits None
Rabbits can browse the fronds without physiological harm. Offer it as one element of a varied diet rather than the sole forage.
Livestock None
Cattle, goats, and sheep are not poisoned by this fern and may share a shaded paddock with it safely.
Birds None
Birds face no toxic hazard from the plant, whether they roost in the fronds or peck at one.
People None
The fern is safe to handle and to grow around children. The only real consideration is mechanical: the fronds and spores can scratch or irritate sensitive skin, so wash your hands after pruning.
Fronds and spores may cause mild mechanical irritation in sensitive individuals; wash hands after handling.
Varieties
Beyond the type species, several selections are valued for the way their fronds twist, ripple, and flare. The forms below are the ones worth knowing.
'Crispum'
A well-regarded ornamental selection identified by strap-shaped fronds whose margins are strongly frilled and crisped into tight waves.
'Undulatum'
It is recognized by pronounced wavy margins that ripple along the entire length of each blade.
'Angustatum'
It differs from the type in bearing narrower, more strap-like fronds than the plain species.
'Sagittatum'
It is distinguished by a frond base that flares into a marked arrow- or fishtail-shaped lobing.
var. americanum (American hart's-tongue fern)
A rare North American native confined to limestone sinkholes and federally protected, so it is not the form offered through the nursery trade.
How to propagate
This fern can be increased by two methods: dividing an established clump for a quick result, or the slower route of raising it from spores.
DivisionModerate
Late winter to early spring · 2-3 months for divisions; spore-grown plants take 1-2+ years to reach garden size
The most reliable method is division in late winter to early spring. Lift a mature clump once it has developed several crowns, separate those crowns, and expect the divisions to establish over two to three months. Propagation from spores is also possible, sown on the surface of a sterile medium as they ripen and held at about 60°F (15°C), but it is a protracted route, since a spore-grown plant requires one to two years or more to reach garden size.
Myths
Because its fronds are undivided and strap-like, it is not a real fern.
Taxonomically it is a genuine fern. It reproduces by spores, borne in orderly herringbone rows of sori on the frond undersides, notwithstanding leaves that never dissect into the lacy outline commonly associated with ferns.
Hart's tongue fern is endangered and illegal to grow.
The widespread European species is common in cultivation and freely traded for the garden. Only the North American native variety, var. americanum, is rare and legally protected, and that taxon is distinct from the plant sold at nurseries.