Bolboschoenus fluviatilis

Botanical name: Bolboschoenus fluviatilis
Synonyms: Scirpus fluviatilis, Scirpus maritimus var. fluviatilis, Scirpus perviridis
Common name(s): Marsh Clubrush, Kukuraho, Ririwaka, Purua Grass, River Bulrush

About:
A tall robust wetland sedge native to New Zealand and many other parts of the world. This species forms dense colonies from underground rhizomes and tubers and is widely used in wetland restoration and wastewater treatment systems.

Natural habitat:
Freshwater and brackish swamps, estuaries, marshes, tidal streams, lake margins, and poorly drained coastal wetlands.

Growing environment:
Full sun, Wet soils, Shallow water, Freshwater wetlands, Brackish marshes, Pond and stream margins.

Endemic distribution:
Indigenous to New Zealand. Found throughout much of the North Island and in suitable wetland habitats elsewhere in the country. Also native to Australia, New Caledonia, North America, and parts of Mexico.

Height:
1.5–2.5 m tall

Width:
Forms spreading colonies via rhizomes

Flowering:
October–January

Fruiting:
December–May

Uses:

• Wetland restoration
• Stormwater treatment
• Wastewater filtration
• Erosion control
• Wildlife habitat
• Traditional Māori food plant

Appearance:

Growth habit:
A summer-green perennial sedge forming large dense clumps from creeping woody rhizomes with rounded underground tubers.

Stems:
Tall upright triangular culms with smooth ridged surfaces.

Leaves:
Long folded grass-like leaves, green and tapering, with rough margins and midribs near the tips.

Flowers:
Terminal umbrella-like clusters of dull reddish-brown spikelets carried on irregular rays above the foliage.

Fruit:
Small pale cream to dark glossy nuts equipped with bristles aiding dispersal by water.

Ecology:
An important wetland species providing habitat, nesting cover, and food for wetland birds, waterfowl, and aquatic fauna. Rhizomes and tubers help stabilise muddy soils and reduce erosion.

Associated habitats:
Often grows with raupō, oioi, sea rush, jointed rush, sedges, and other freshwater and estuarine wetland vegetation.

How to grow:
Thrives in permanently damp soils or shallow standing water in full sun. Suitable for ponds, constructed wetlands, and tidal margins.

Propagation:
Easily propagated from fresh seed, rhizome sections, or rooted tubers.

Cultural significance:
Some inland populations are believed to have been deliberately cultivated by Māori as a traditional food source due to the edible underground tubers.

Garden value:
Excellent for wetland planting schemes, stormwater systems, pond margins, and ecological restoration projects where strong vertical structure and habitat value are desired.