This article was published in the Titirangi Tatler, November 2010
Libertia -the New Zealand ‘Iris'.
If you are strolling in the Waitakere Ranges, there are 3 species of the native Iris to look out for, and they can best be seen in late spring as they flower. Generally they are found in light forest clearings, along drier ridges, and on coastal cliffs. They all develop fan-shaped clusters of erect, spiky green leaves with slender flower-stalks producing clusters of white flowers, each with three petals. There was once a fourth species growing at Piha, but it is now presumed regionally extinct as it has not been seen for many years.
Libertia is the only New Zealand genus in the worldwide Iris family. There are eight species in New Zealand and half of them have only recently been identified as being distinctive. The most recent, Libertia flaccidifolia (2009) is distinctive because of its more drooping (flaccid) foliage in mature plants. It has been located only on the slopes of Mt Tamahunga near Warkworth. It is a good example of the process scientists are going through as more knowledge increases our ability to distinguish local variations in plants.
The other 3 newly-described species (2002) were named to honour three prominent lady botanists of the mid-20th century, Lucy Cranwell, Elizabeth Edgar and Lucy Moore. The species grow in confined areas: Libertia cranwelliae on the East Cape, Libertia edgariae around Wellington, while Libertia mooreae has a slightly wider distribution on both sides of Cook Strait.
The 4 species originally identified had a much wider distribution, with Libertia ixiodes common throughout the country. Libertia grandiflora is found only in the North Island but is also quite common. It differs from Libertia ixioides by having taller flower stalks that hold the flowers above the foliage. The other two species are less common, with Libertia peregrinans now regarded as nationally vulnerable. Having once been found throughout the country, its stronghold is now on the Chatham Islands. The last and smallest of the species is Libertia micrantha which grows on mountains and colder sites throughout. In the Waitakeres it is confined to colder areas in gullies.
There are two growth forms in the Libertia genus with L. peregrinans and L. cranwelliae having spreading rhizomes and quite orange colouring in the leaf blades. The other species all have a tight, clump-forming growth habit and generally much greener foliage.
Libertia are popular in modern gardens and can be seen on many roundabouts and median strips as they are low-maintenance plants that can look good for many years. A curious feature is their fibrous, tough leaf structure. It evolved no doubt to resist moa browsing, and it continues to be useful in situations where resistance to animal damage is needed, e.g. the browsing of geese in Dublin's zoo.