Manawa

Botanical name: Avicennia marina subsp. australasica
Synonyms: Avicennia resinifera, Avicennia marina var. resinifera
Common name(s): Manawa, mangrove, grey mangrove, white mangrove

About:
New Zealand’s only native mangrove species. A highly specialised coastal tree adapted to life in tidal estuaries and mudflats through salt-filtering roots, salt-excreting leaves, and aerial breathing roots known as pneumatophores.

Natural habitat:
Occurs naturally in sheltered estuaries, tidal river flats, shallow harbour margins, mudflats, and coastal inlets with muddy or silty substrates.

Growing environment:
Full sun, Coastal wetlands, Brackish tidal zones, Muddy estuarine soils, Salt tolerant & Frost sensitive when young.

Endemic distribution:
Indigenous to northern New Zealand from Parengarenga Harbour south to Kawhia and Ohiwa Harbours. Also occurs naturally in Australia and across the Indo-Pacific region.

Height:
Usually 1–12 m tall depending on conditions

Width:
Can form broad spreading groves several metres across

Flowering:
February–April

Fruiting:
December–January

Uses:

• Coastal stabilisation
• Estuary restoration
• Sediment trapping
• Fish nursery habitat
• Shoreline protection
• Wildlife habitat

Appearance:

Growth habit:
A spreading coastal tree or shrub forming dense intertidal forests or low shrubby thickets depending on salinity and exposure.

Roots:
Produces extensive underground cable roots with numerous upright pencil-like pneumatophores that protrude above the mud surface to absorb oxygen.

Bark:
Grey and furrowed on mature trees with stout brittle branches.

Leaves:
Leaves are opposite, leathery, glossy dark green above and pale grey-green or silvery beneath due to dense fine hairs. Salt crystals are often visible on the leaf surface.

Flowers:
Small orange-yellow flowers borne in clusters near branch tips and upper leaf axils.

Fruit:
Large leathery yellowish seed capsules that often partially germinate while still attached to the tree before floating away on tides.

Ecology:
An ecologically critical estuarine species that traps sediment, stabilises mudflats, filters runoff, and provides important nursery habitat for fish, shellfish, crabs, and coastal birds.

Associated habitats:
Frequently associated with estuarine mudflats, tidal channels, saltmarsh communities, seagrass beds, and coastal wetland ecosystems.

How to grow:
Best grown in permanently damp coastal soils or shallow brackish water in full sun. Young plants establish readily from fresh propagules or partially germinated fruit.

Propagation:
Easily grown from ripe floating fruit which usually germinate naturally soon after dispersal. Plants transplant readily while young.

Cultural significance:
Traditionally significant to Māori as an important coastal species associated with sheltered harbours and estuarine food-gathering areas. Mangrove ecosystems remain culturally and ecologically important throughout northern New Zealand.

Garden value:
Suitable only for specialised coastal wetland or restoration plantings. An outstanding species for estuary rehabilitation, sediment control, and coastal biodiversity enhancement in northern New Zealand.