Deparia Fern

Botanical name: Deparia petersenii subsp. congrua
Synonyms: Athyrium japonicum sensu Allan; Deparia tenuifolia; Diplazium congruum; Diplazium japonicum; Athyrium congruum; Athyrium japonicum sensu Dobbie
Common name(s): Deparia Fern

About:
Deparia petersenii subsp. congrua is a fast-spreading terrestrial fern recognised by its long creeping rhizomes, fresh yellow-green fronds and distinctive unpleasant aroma when the foliage is crushed. It is commonly found in damp, disturbed forests, stream margins and forest edges, where it readily forms extensive colonies. Although indigenous to New Zealand, it is also naturally distributed across much of the Pacific and eastern Australia.

Natural habitat:
Coastal to lowland forest, river flats, forest margins, damp gullies, disturbed bush, rough pasture, willow carr, urban bush remnants and other moist, semi-shaded environments.

Growing environment:
Thrives in moist, fertile soils with partial to heavy shade. It tolerates a wide range of growing conditions provided adequate moisture is available and often colonises disturbed ground.

Endemic distribution:
Indigenous to New Zealand. Found on Raoul Island in the Kermadec Islands, throughout much of the North Island from Te Paki south to Wellington, and in the South Island as far south as the West Coast near Hokitika. Also occurs naturally in eastern Australia, Norfolk Island, Malesia and many Pacific islands.

Height:
20–90 cm

Width:
Spreads indefinitely by long creeping rhizomes.

Flowering:
N/A – ferns do not flower.

Fruiting:
Spores are produced on fertile fronds, mainly during the growing season.

Uses:
• Native fern gardens
• Moist woodland plantings
• Riparian restoration
• Groundcover in shaded areas
• Naturalistic forest gardens
• Erosion control on damp banks

Appearance:
Growth habit:
A terrestrial fern with long-creeping rhizomes that produce numerous upright fronds, allowing it to rapidly form extensive colonies.

Rhizomes:
Rhizomes are slender, creeping and scaly, typically 2.5–7 mm in diameter. Golden-brown scales cover the rhizomes and help distinguish the species.

Fronds:
Fronds are yellow-green to green, soft but brittle, and usually 20–90 cm long. They are once- to twice-divided, with the larger lower pinnae deeply lobed into rounded or oblong segments. The fronds bear numerous fine hairs and scattered scales and emit a noticeable unpleasant smell when bruised.

Stipes:
Frond stalks are yellow-brown to dark brown, slightly swollen at the base and bear numerous scales and multicellular hairs. The upper stalk and rachis become green towards the frond.

Flowers:
No flowers are produced.

Fruit:
No fruit is produced. Spores develop within elongated sori on the undersides of the fronds.

Sori:
The sori are long and narrow, arranged along the veins in a distinctive herringbone pattern. Many occur in paired back-to-back rows, a useful feature for identification.

Ecology:
This fern is an early coloniser of disturbed forest and moist clearings. It spreads rapidly by creeping rhizomes and wind-dispersed spores, helping stabilise damp soils while providing shelter for small forest invertebrates.

Associated habitats:
Lowland podocarp forest, broadleaf forest, riparian margins, damp gullies, willow carr, forest tracks, roadside cuttings and urban bush remnants.

How to grow:
Plant in moist, fertile soil in partial or full shade. It appreciates regular moisture but adapts to a wide range of conditions once established. In cooler districts the fronds may die back during winter before reshooting strongly in spring. Because of its vigorous spreading habit, allow sufficient space or contain it where necessary.

Propagation:
Very easily propagated by dividing established rhizomes. It is also readily raised from fresh spores and frequently self-establishes naturally in suitable gardens.

Cultural use:
There are no widely documented traditional Māori uses for this fern, although it forms an important component of many indigenous forest ecosystems throughout northern New Zealand.

Garden value:
An excellent fern for quickly establishing lush groundcover beneath trees or in damp shaded gardens. Its bright foliage provides strong textural contrast among other native ferns, although its vigorous growth means it is best suited to larger gardens or naturalistic restoration plantings where it has room to spread.