Swamp forests are dominated by kahikatea, New Zealand’s tallest tree. In wet conditions it produces long, spreading roots, and the trunk is usually buttressed for support.
Other common plants of the wetland forests include:
- Pukatea and swamp maire. These trees often grow in association with kahikatea, in the North Island and the top of the South Island. Both produce pneumatophores (breathing roots) that rise above the ground.
- Cabbage trees. Before human settlement, these grew at the edge of swamp forests and on river plains. They formed a narrow band between rush and sedgelands, growing near open water and forest on more elevated land. As people cleared the forests and lit fires, cabbage trees thrived – they are ‘pioneer’ plants, regenerating well in open conditions.
- Silver pine and yellow-silver pine. These small native conifers tend to dominate forests of infertile bogs. They often grade into shrublands containing bog pine, pink pine, celery pine and mānuka.
- Willow. Eleven species and hybrids of willow (non-natives) were introduced to stabilise river banks. They have spread into wetlands alongside rivers and lakes. Grey, pussy and crack willow have achieved weed status and infest fertile swamplands.
Mānuka is a common shrub of wetlands. Its roots tolerate submersion for long periods.
Small-leaved divaricating shrubs are often associated with wetlands, especially on valley floors. Mingimingi (Coprosma propinqua) is particularly common, but a number of coprosma species may be present, along with Olearia virgata, swamp broom (Carmichaelia arborea), and swamp māhoe (Melicytus micranthus).
The heath family (Ericaceae) is well represented on peat bogs and infertile wetlands. Included here are snowberry (Gaultheria depressa), inaka (Dracophyllum longifolium, D. lessonianum and the Chatham Island D. scoparium), and Epacris pauciflora.