Thousand-leaved fern
Botanical name: Hypolepis millefolium
Synonyms: None commonly accepted
Common name(s): Thousand-leaved fern
About:
A finely divided, bright green endemic fern with delicate, almost lace-like fronds and a long-creeping underground rhizome. Hypolepis millefolium is one of the more attractive New Zealand members of the genus and is usually associated with montane, subalpine and alpine habitats.
The fronds are brittle, finely dissected and generally smaller and more delicate than those of Hypolepis ambigua. Unlike many other Hypolepis species, it is relatively long-lived, less aggressively weedy and often deciduous during winter.
Natural habitat:
Coastal to alpine, although in the northern part of its range it is mainly confined to montane and alpine environments.
Occurs in tussock grassland, herbfield, rocky slopes, shingle slides, shrubland, open hillsides, pasture, forest margins, clearings, streambanks, swamp margins and road banks.
It also grows within podocarp, broadleaf and beech forest, mānuka scrub and beneath conifer plantations.
Growing environment:
Frost, Sun, Partial Shade, Wind, Cool Conditions & Free draining tolerant. Prefers cool, open or lightly shaded sites with reliable moisture.
Endemic distribution:
Endemic to New Zealand.
Found in the North Island from Mt Pirongia and East Cape southward, especially through the Central Volcanic Plateau, Mt Taranaki and the main axial ranges.
Widespread through the South Island, and also present on Stewart Island/Rakiura, the Chatham Islands, Antipodes Islands, Auckland Islands and Campbell Island/Motu Ihupuku.
Height:
Fronds commonly approximately 20–80 cm long, occasionally approaching 1 m.
Width:
Individual fronds commonly 8–40 cm wide.
Colonies can spread widely by underground rhizomes.
Flowering:
Not applicable — fern species reproducing by spores.
Fruiting:
Not applicable — spore producing.
Rounded sori develop on the lower surfaces near the margins of the ultimate frond segments.
Uses:
• Alpine and subalpine fern gardens
• Native rock gardens
• Tussock and herbfield plantings
• Cool-climate fern borders
• Naturalistic restoration planting
• Forest-edge planting
• Groundcover in larger native gardens
Appearance:
Growth habit:
A terrestrial fern spreading from slender, long-creeping subterranean rhizomes approximately 1.5–4 mm in diameter.
Fronds arise at intervals along the rhizome and may form extensive colonies.
Leaves:
Fronds are vivid bright green to yellow-green and finely divided, giving the species its “thousand-leaved” appearance.
The lamina is ovate to broadly ovate or elliptic, typically three to four times divided and occasionally almost five times divided near the base.
Fronds usually reach approximately 85–770 mm long and 35–400 mm wide.
Primary pinnae are numerous and usually longest below the middle of the frond. Secondary and tertiary pinnae are progressively smaller and broadly winged.
Ultimate segments are very narrow, generally less than 1 mm wide.
The frond bears sparse glistening colourless or pale brown hairs along the costae and midribs, but glandular hairs are absent.
Flowers:
None.
As a fern, Hypolepis millefolium does not produce flowers or seeds.
Fruit:
None.
Spores develop in rounded sori positioned close to the margins of the ultimate segments.
The sori are usually uncovered or only partly protected by a slightly reflexed green marginal flap.
Unlike some related species, hairs are absent from the sori.
Spores are pale brown and echinate.
Ecology:
Hypolepis millefolium is strongly associated with cool open habitats and higher elevations.
Its creeping rhizomes allow it to spread through tussock grassland, rocky slopes and disturbed alpine ground, where it may form large colonies.
In southern New Zealand and the Subantarctic islands it descends to very low elevations and sometimes near sea level.
The fern is typically winter-deciduous, with fronds dying back during cold conditions and fresh growth emerging again during the warmer growing season.
Its minute spores are dispersed by wind.
Associated habitats:
Tussock grassland, alpine herbfield, subalpine scrub, shingle slopes, rocky hillsides, stream margins, swamp margins, forest margins, beech forest, podocarp forest, broadleaf forest, mānuka scrub, peat bogs and Subantarctic grasslands.
How to grow:
Relatively easy to cultivate compared with many native alpine ferns.
Grow in full sun to partial shade in a cool position with moist but well-drained soil.
It performs particularly well in rock gardens, fern borders and naturalistic tussock plantings.
Although naturally associated with high elevations, it can be grown successfully at lower elevations where summer heat and humidity are not excessive.
Winter dieback is normal in colder areas.
Propagation:
Easily propagated from fresh spores.
Spores should be sown on a sterile, moist fern medium and kept humid until young plants establish.
It can also be propagated from rooted rhizome pieces.
Division is usually straightforward because the underground rhizomes naturally produce multiple growing points.
Cultural use:
No specific traditional Māori use is widely documented for Hypolepis millefolium.
The specific epithet millefolium comes from Latin words meaning “thousand-leaved” or “many-leaved”, referring to the extremely finely divided fronds.
Garden value:
One of the most attractive New Zealand Hypolepis species.
Its bright green, finely dissected fronds provide a soft, delicate texture that contrasts strongly with coarse tussocks, rocks and larger native ferns.
Because it is less invasive and generally longer-lived than species such as H. ambigua and H. dicksonioides, it is particularly suitable for native fern gardens, alpine plantings and cooler landscape settings.