Ohinetahi stands at the head of Lyttelton Harbour. The first known house, Rosemary Cottage (named after one of Bishop Selwyn's daughters), was reputed to be the first design in New Zealand of the architect Benjamin Mountfort (1825-1898). It was built by Christopher Alderson Calvert (1811-1883) in 1851. Calvert was a lawyer who had come to Canterbury on the 'fifth ship', the Castle Eden, in 1851. On consulting Maori about a name for the area, they suggested and he adopted, Ohinetahi. Over the next five years or so there were five other owners, the last being William Sefton Moorhouse (1825-1881) who sold the property, then of 225 acres, to Thomas Henry Potts (1824-1888), an eminent botanist and ornithologist, in 1858. Moorhouse is credited with adding the timber wings to the existing house.
Potts pulled the two timber wings further apart in the 1860s, adding a more substantial three-storey structure of locally quarried sandstone, with a verandah all round. A succession of owners followed and the structure fell into disrepair. A Christchurch architect, Sir Miles Warren, and John and Pauline Trengrove bought it in 1977 and undertook its restoration. Additions in the 1990s included a housekeeper's cottage, a tower from which the house and garden might be viewed and an art gallery set below, beside the rose garden, facing the sea.
A garden was first made in 1865 by Potts, who planted a great variety of exotic trees and shrubs chosen on the advice of Kew Garden authorities. Many of these still stand on the perimeter of the garden. After he died in 1888 the garden was neglected until it consisted of little more than a lawn around the house. Sir Miles began the present garden in 1977, assisted by his sister, Pauline Trengrove (a painter) and her husband John (an architect). Over a period of 19 years they transformed the remnants into one of New Zealand's most celebrated gardens, covering 1 1/4 hectares. The formal garden consists of a number of separate garden rooms of differing style and character arranged about two axes running east-west and north-south. Between the house and the western boundary is a ravine that has been made into a bush garden.