Giant hypolepis
Botanical name: Hypolepis dicksonioides
Synonyms: Hypolepis tenuifolia sensu Hook.f., Hypolepis tenuifolia var. pellucida, Cheilanthes dicksonioides, Cheilanthes pellucida, Hypolepis endlicheriana
Common name(s): Giant hypolepis, Ground fern
About:
A very large, fast-growing fern with broad, bright green, highly divided fronds and a distinctive sticky surface created by abundant glandular hairs.
Hypolepis dicksonioides is usually the largest New Zealand member of the genus and can produce spectacular fronds well over 2 m long in favourable conditions. The sticky hairs frequently trap insects, feathers, dust and other debris, making mature fronds easy to recognise.
It is naturally short-lived and opportunistic, appearing where disturbance creates fresh open habitat, including geothermal ground, slips, roadsides, forest margins and urban sites.
Natural habitat:
Coastal to lowland, extending into montane geothermal areas.
Found on rocky coastal slopes, cliff bases, boulder fields, sandy ground, scoria, pumice beds, geothermal soils, hot stream margins, roadsides, ditches, poor pasture, forest clearings and margins, old logs and beneath pine plantations.
It strongly favours recently disturbed or open ground.
Growing environment:
Sun, Partial Shade, Warmth, Disturbed Soil & Free draining tolerant. Frost tender, although established rhizomes may survive winter and reshoot.
Endemic distribution:
Indigenous but not endemic to New Zealand.
Found on the Kermadec Islands, Manawatāwhi / Three Kings Islands, North Island, Chatham Islands and locally in northern parts of the South Island, including north-west Nelson and the Marlborough Sounds.
Also occurs on Norfolk Island, Samoa, the Cook Islands, Tahiti and the Marquesas Islands.
Height:
Fronds commonly 0.2–2.4 m long.
Width:
Large fronds may exceed 1.3 m wide.
Colonies may spread widely through long-creeping rhizomes.
Flowering:
Not applicable — fern species reproducing by spores.
Fruiting:
Not applicable — spore producing.
Round sori develop near the margins of the ultimate frond segments.
Uses:
• Large fern displays
• Geothermal and subtropical-style planting
• Naturalistic fern gardens
• Rapid colonisation of disturbed ground
• Forest-edge restoration
• Large-scale revegetation where spread can be controlled
Appearance:
Growth habit:
A robust terrestrial fern spreading from long-creeping rhizomes approximately 3–8 mm thick.
Stipes arise at intervals along the rhizome, often producing widely spaced but enormous fronds.
Leaves:
Fronds are bright to light green, broadly ovate to broadly elliptic and usually three to five times divided.
The lamina may reach approximately 1.5 m long and 1.3 m wide, with exceptionally large wild specimens exceeding this.
Primary pinnae are numerous and often largest toward the base. Secondary and tertiary pinnae are progressively divided into increasingly fine ultimate segments.
The stipe is thick, usually 2–15 mm in diameter, red-brown toward the base and yellow-brown above. Two dark longitudinal bands are often visible on fresh stipes.
The frond surfaces, rachis and stipe carry abundant colourless glandular and non-glandular hairs.
These glandular hairs make young and mature fronds noticeably sticky.
Flowers:
None.
As a fern, Hypolepis dicksonioides does not produce flowers or seeds.
Fruit:
None.
Spores are produced in rounded sori positioned near the upper margins of the ultimate segments.
Each sorus is protected from an early stage by a conspicuous reflexed flap of the lamina.
These indusial flaps are green toward the base and membranous toward the outer edge.
Ecology:
Hypolepis dicksonioides is an ephemeral pioneer species that depends heavily on disturbance.
Its spores readily colonise bare or recently disturbed substrates such as geothermal ground, slips, pumice, scoria, exposed soil and urban rubble.
Plants may appear suddenly, grow rapidly, reproduce, and then disappear as competing vegetation closes over the site.
On some offshore islands, especially Macauley Island in the Kermadec group, it can dominate large areas of vegetation.
Wind-dispersed spores allow it to reach isolated newly disturbed habitats efficiently.
It frequently hybridises with Hypolepis ambigua in geothermal areas where both species occur together.
Associated habitats:
Coastal scrub, open forest, geothermal vegetation, pumice fields, scoria, cliff bases, rocky slopes, roadsides, poor pasture, drainage ditches, pine plantations, forest margins, old logs and disturbed urban ground.
How to grow:
Easy to cultivate but potentially invasive.
It grows readily in warm, sheltered sites with moist but well-drained soil and performs in full sun to partial shade.
Because of its large size and rapidly spreading habit, it needs considerable space and is unsuitable for confined garden beds.
Plants are naturally short-lived but often regenerate freely from spores if suitable bare substrate remains nearby.
Protect from severe frost. Established plants may die back during winter but can sometimes reshoot from protected rhizomes.
Propagation:
Very easily propagated from fresh spores.
Sow spores over a sterile, moist fern medium and maintain high humidity until young sporophytes establish.
Once mature plants begin producing spores, self-seeding may become prolific.
Because of its potential to become weedy, propagation should be undertaken only where its spread can be managed.
Cultural use:
No specific traditional Māori use is widely documented for Hypolepis dicksonioides.
The genus name Hypolepis derives from Greek words meaning “under” and “scale”, referring to the position of the sori.
Garden value:
A spectacular but vigorous fern best suited to large gardens, ferneries and naturalistic landscapes.
Its huge, finely divided bright-green fronds provide a lush subtropical appearance, while the sticky glandular surfaces and strongly deltoid outline make it botanically distinctive.
Its size, vigorous colonising ability and tendency to self-seed mean it should be used carefully, but where space allows it can be one of the most impressive native ground ferns.