The plant communities of a lowland alluvial floodplain in south Westland were classified on the basis of floristic composition from ninety eight vegetation descriptions. Five forest, one scrub, and two mire/swamp communities were identified. Plant communities were distributed in relation to landform types and soil properties. Different landforms were dominated by different plant communities and were characterised by broad soil types that reflected the nature of the landforms and the processes ofsoil development. Alluvial deposition and surface age were identified as important factors influencing the soil and vegetation patterns across landform types.