The widespread and locally common liane pohuehue (Muehlenbeckia australis) is endemic to New Zealand and Norfolk Island. It is one of five indigenous species of this genus in New Zealand amongst twenty species distributed from South America to Australia. They belong to Family Polygonaceae – the dock family – a cosmopolitan family of shrubs, herbs and lianes.
In the New Zealand context pohuehue is found from the coast through lowland regions to montane sites in hill-country and shrubland areas. This widespread liane can grow to about 10 metres tall as it winds it way up forest or forest remnants. It is a deciduous species with larger leaves than its New Zealand relatives. Patches of pohuehue can be many square metres in extent, and are typically one to two metres above ground climbing over and completely covering the supporting vegetation.
My longterm observations of sites close to Dunedin show that in this way it nurtures the supporting and regenerating vegetation it covers, allowing over time these species to push through the cover of pohuehue and dominate at some later time. I have seen the indigenous trees wineberry, mahoe and fuchsia regenerate within a pohuehue-dominated cover over a period of 15 years.
Ecologically it is an important native species, if not the most important species in many contexts, as it is able to survive if not thrive when sites are disturbed by felling, clearance or fire. Often it is the only native species left following gross disturbance of indigenous vegetation. Riparian sites, gullies, hillsides and roadsides across the Canterbury Plains showcase the 'staying power' of this wonderful New Zealand native liane. If left to 'dominate' these sites it will nurture whatever indigenous species are left on the site as stragglers or seeds, and eventually give way to these taller species. Typically M. australis is a marginal species, covering the edge of forest or shrubland patches and protecting forest edges from the ravages of wind damage. Without its survival in these disturbed landscapes many indigenous insects would not be able to survive there and provide food for indigenous reptiles and birds.
From and entomological perspective pohuehue/Muehlenbeckia australis is the single most important hostplant with tens of indigenous insects depending on it, many of which also feed on its sister species M. complexa. It supports diverse Orders of insects such as our sole praying mantis, many stick insects, myriad flies, lacewings, wasps, bugs, moths, butterflies and beetles. Amongst the butterflies and moths it is the most eaten New Zealand plant supporting many groups of these insects as follows. These include both specialists and species that feed on other indigenous plants in addition to pohuehue:
Overall pohuehue is the most important indigenous New Zealand plant for our indigenous insects, particularly moths and butterflies. Together with its ecological importance of both survival and nurturing, is assumes fundamental importance across our landscapes both natural and disturbed.
Author: Dr Brian Patrick, Wildlands, Christchurch, 18 May 2016.
Photos by Alice Shanks
Top: Copper butterfly
Bottom: Pohuehue/Muehlenbeckia australis