Some native plants have been improved as garden specimens by breeding. The colourful hebes, mānukas, flaxes and cabbage trees that are popular are man-made creations.
The hebe group has nearly 100 species. During the mid-1800s, British nurserymen began to take advantage of the great tendency for hebe species to breed together. The offspring of two species is called a hybrid. Hebe ‘Andersonii’ was the first artificial hybrid, raised in Edinburgh in 1849. Since then over 800 cultivars (cultivated varieties) and hybrids have been created, mainly by British and French breeders. However, Jack Hobbs, a New Zealand breeder, has overseen the development of about 20 cultivars, including the popular ‘Wiri’ series.
There are two species of New Zealand flax: harakeke (Phormium tenax) and wharariki or mountain flax (Phormium cookianum). They are clump-forming plants with fans of sword-shaped leaves. Māori recognised different forms, which they grew for weaving and rope-making. They also selected naturally occurring coloured and variegated forms, for ornament. The two flaxes hybridise easily. Walter Brockie bred the first red-leaved cultivars ‘Aurora’ and ‘Smiling Morn’ in 1940.
Gardeners have since bred many cultivars, from the small, purple ‘Platt’s Black’ to the 3-metre grey-green ‘Goliath’. New Zealand breeders are continuing to develop compact, multi-hued cultivars.
Mānuka (Leptospermum scoparium) is one of New Zealand’s commonest native shrubs. It typically has single white flowers, but sometimes double and red-flowering forms arise. The first red cultivars, such as ‘Nichollsii’ and ‘Keatleyi’, were selected from plants with naturally occurring red flowers.
In 1939, a Californian geneticist, W. E. Lammerts, crossed a red mānuka with a double-flowered pink mānuka, producing a range of attractive flowering cultivars, notably ‘Red Damask’.
A year or so later, Duncan & Davies released the ‘Nanum’ mānuka cultivars – 12 dwarf and semi-dwarf selections that came from a plant growing on the Volcanic Plateau.
Serious systematic breeding of mānuka in New Zealand began in the 1980s and 1990s. Scientists crossed cultivars with Australian Leptospermum species, in the hope of raising some lines that would be suitable for the cut-flower trade. Jack Hobbs introduced the ‘Wiri’ series of dwarf and semi-dwarf mānuka. Warwick Harris from Landcare Research collaborated with the French breeder Luc Decourtye in investigating the cold-hardiness of selected lines of mānuka.
The flurry of systematic breeding of natives in the 1980s stopped in the 1990s. It is expensive to fund shrub and tree hybridisation programmes, which must run for two or more generations. Some breeders failed to secure funding, and some became wary of working with native plants while the Waitangi Tribunal hearing into the Indigenous Flora and Fauna of New Zealand – the Wai 262 Claim – remained unresolved. Under this claim Māori assert that the Treaty of Waitangi guarantees them ownership rights to indigenous plants and the genetic material they hold.