There are several mature New Zealand plants in the garden that were planted in the 19th Century. Podocarpus totara, Podocarpus hallii, Griselinia littoralis and several Nothofagus spp. are all record sized specimens in the UK.  GRG Carlyon who was born in NZ and emigrated to Cornwall was a terrific plantsman and collector and imported many seeds from his homeland. He sourced much material for Tregrehan from his birthplace at Gwavas Station in Hawkes Bay. There the family has preserved 150 Ha of original lowland Podocarp forest which is a rare item with the wholesale clearance of this type of NZ bush country.

The original Gwavas homestead has been restored by Phyl and Stu Gibson to provide accommodation and entertainment facilities. The surrounding 10 Ha garden was started by ASG Carlyon in the 1880's and has been continually planted and is now maintained by Michael Hudson. It has been awarded a conservation plaque by the International Dendrology Society, one of only about 20 in the world, in recognition of the class of the plant collection.

Tom Hudson probably as a result of emigrating from NZ to Cornwall has also planted a collection of NZ plants. A separate area within the Gondwanaland part of the garden has been set aside for woody trees and shrubs from mid altitude NZ forest. The mixed broadleaf and coniferous tree mixture is virtually all evergreen so eventually there will be little light for the understory layer. Treeferns spore in the damp areas naturally and lianas and prickly rubus ramble right up into the crowns of the larger trees.