The vegetation of an area of the Upper Clutha basin, New Zealand, with a 'semi-arid' climate, was sampled with 95 quadrats in a nested randomised design. All types of vegetation were sampled, from near-natural to managed pastures. Twenty four environmental factors were measured in each quadrat. Five 'formations' are described, and 14 'communities' recognised within them, although there are few constant or faithful species. Such weak structure, and relatively weak correlation with the environment, are partly attributed to non- equilibrium.