Libertia Cranwelliae - Confirmed From the Wild After 43 Years
Cranwell’s Iris/Mikoikoi (Libertia cranwelliae) was formally described in 2002 in the New Zealand Journal of Botany by Dr(s) Dan Blanchon, John Braggins and Brian Murray. That paper was the conclusion of Blanchon’s PhD investigation into the genus Libertia. His new species L. cranwelliae was then known in cultivation as a “rhizomatous form” of L. ixioides. Blanchon’s research showed that it was a true-breeding, morphologically and cytologically distinct species, which appears to have evolved through past hybridism between L. ixioides and L. peregrinans. It is distinguished by the combination of having a dodecaploid chromosome number (2n = 228), elongate, yellow rhizomes, small ovaries, long, straight, green leaves with yellow bases, and inflorescences immersed within the foliage rather than overtopping it. The new species was then only known from a handful of herbarium collections made from the north-eastern coastline of East Cape, the last of which came from the Kopuapounamu Valley in 1965. Libertia peregrinans - so popular in cultivation - is now not known from the East Cape (nor, in fact, any of the eastern coastline of the North Island), though L. ixioides is common in this area.Most of Blanchon’s research on this species was necessarily based on a single garden clone that appears to have stemmed from a plant collected by Norman Potts of Opotiki from the Kopuapounamu Valley and cultivated at Hikutaia Domain. This was because no wild plants could then be found. Later limited field survey, especially in the Kopuapounamu Valley and Awatere River, East Cape - the last known locations for L. cranwelliae - by the then Gisborne based DoC botanist Mike Thorsen and Wildlands Consultant Karen Riddell failed to find any more plants. However, it was believed too early to record it as extinct.
Three years ago DoC East Cape Ranger Graeme Atkins found an unusual Libertia near East Cape. Wondering what it was , he took seed pods off the plants. Two weeks ago Gisborne based DoC Technical Support Officer Dave Carlton who suspected Atkin’s plant was the long-lost L. cranwelliae sent material to DoC’s threatened plant botanist Peter de Lange for examination. Initially de Lange was unsure. The specimen was clearly rhizomatous - a feature of L. cranwelliae - but differed somewhat with respect to leaf colour and stature. Therefore, he took the material to the now Auckland, Carrington Unitech based, botanist and lecturer Dan Blanchon for a second opinion. Both botanists were then able to confirm that Atkin’s mystery Libertia was indeed L. cranwelliae.
Currently Libertia cranwelliae is listed as “Data Deficient” because no one had seen it for 43 years and with so little information, making an accurate call on its conservation status was considered impractical. Atkins’s find will go some way to improving our knowledge of this unusual plant. Not only do we now know of one surviving population but we also have a better idea of where to look. Unfortunately the population Atkins found is very small (c.30 plants) and is in an area that is now overrun by goats, cattle and red deer. With such a small population, and one under active threat L. cranwelliae may merit listing as “Threatened/Nationally Critical”. However, East Cape is a large area, and now that people know what they are looking for it is hoped further populations will be found.
Posted: 29/06/2008