February in the hills with Chris Horne
Muehlenbeckia australis agg, pōhuehue, puka, large-leaved muehlenbeckia
Origin of the names
Muehlenbeckia is named after the Alsatian physician and botanist, Heinrich Gustav Muehlenbeck (1798-1845); australis means ‘southern’; ‘agg.’ indicates that the form of the species is variable. Pōhuehoe, or pōhue, are Te Reo names for several species of climbing or trailing plants; puka is a Te Reo name for several species with large leaves.
Distribution and habitat
Pōhuehue is native to New Zealand, but not endemic, because it also grows on Norfolk Island. It grows on Manawatāwhi/The Three Kings, Te Ika a Māui/North Island, Te Waipounamu/South Island, Rakiura/Stewart Island, and Rekohu/Chatham Islands. Look for pōhuehue in lowland to montane forests, often on their edges.
Pōhuehue, a member of the dock family, is a stout liane/climber up to 10 m tall with many branches which are more or less interlacing. The result, in the absence of a tree for it to climb, is a much-tangled mass on and near the ground. The main stem, up to 10 cm diameter, is round in cross-section, has grey bark and is often grooved. The dark-grey branchlets are slender, circular in cross-section, and often grooved.
The leaves are 2-8 cm long x 1-3 cm wide, thin, dark green above, paler green below, egg-shaped to oblong, often with a ‘waist’ or three lobes, and pointed tips. All forms may be on the same plant. The edges of the leaves are smooth and often wavy. Pōhuehue is sometimes deciduous so you may see it devoid of leaves in winter.
When it climbs a sapling, pōhuehue spirals up the host and may deform the host’s trunk, creating a helix-shaped groove on it. Unlike most other climbers, pōhuehue may spiral clockwise or anti-clockwise.
Pōhuehue’s foliage sometimes smothers the crowns of trees on the edges of regenerating forest and weighs down, or even snaps, their branches. It is therefore sometimes considered to be a weed. On the other hand, in scrambling over trees, it can reduce the effects of gales on the trees on bush edges and limit the drying out of a native plant community caused by gales, direct sunlight and by drought.
Pōhuehue is dioecious, meaning that female flowers and male flowers grow on separate plants. The numerous flowers are greenish, 4-5 mm in diameter, and about 5 mm long. They grow in clusters up to 15 cm long x 10 cm wide. Pōhuehue flowers and fruits from November to April, and sometimes as late as June. The seeds, about 3.5 mm long, are black, glossy, three-sided, and enclosed by persistent sepals which sometimes become white and fleshy. The wind spreads pollen from male plants to female plants and birds spread the seeds.
In 1868, Colenso reported that the swollen flowers were a popular food with Māori children. Try eating the sepals and sample their sweetness! The vines have been used to make hīnaki/fish traps.
Value for our flora and fauna
Pōhuehue is of fundamental importance to our ecology. It nurtures the regenerating vegetation which it clambers over, enabling those young trees, e.g. māhoe, wineberry, māpou, to penetrate it and eventually dominate it. It is often the only native species to survive following gross disturbances e.g. felling, fire or clearance. As it grows over a devastated site, seeds blown into it or dropped into it by birds are able to germinate. The resulting seedlings grow up through it, so it acts as a ‘nurse crop’ for a forest to replace the one that was destroyed. Birds, skinks and geckos eat the sweet-tasting sepals on female plants. Its presence enables many species of native insects, including butterflies and moths, to survive. The larvae of some moth species are leaf-rollers on pōhuehue, while those of other species make leaf mines in which they feed. (More information: Open Space. Issue 91. October 2016. QEII National Trust. Article by Brian Patrick, Wildlands Consultants.)
Where to find pōhuehue
Pōhuehue is abundant in Wellington city’s reserves, particularly on bush edges. It is also common in private gardens. Look for pōhuehue in the Tararua, Remutaka and Aorangi ranges, and in many other forests.