Rimu is the commonest and most widely distributed conifer in New Zealand, growing from Northland down to Stewart Island. It is a tall tree, and its crown usually emerges above the main canopy of forest trees. On well-drained fertile sites, it grows to 50 metres in height. Rimu usually favours better drained sites than kahikatea, but does grow in poorly drained soils in Westland.
Rimu can live for more than 1,000 years. A life-span of 550–650 years is more common, as old trees become susceptible to uprooting in strong winds. Seedlings will not grow in deep shade or on open, exposed sites. Mature trees often support a crop of perching plants on their upper branches. For example, northern rātā often starts life as a young seedling high up in the crown of a mature rimu.