October in the hills with Barbara Mitcalfe and Chris Horne
Hoheria sexstylosa, houhere, a lacebark species
Hoheria sexstylosa is the only naturally-occurring Wellington lacebark species. Houhere is the Māori name for all lacebarks, and the source of their generic name. NZ's endemic genus Hoheria is a member of the worldwide Malvaceae (mallow) family. Most of them have tough fibres in their stems or leaves, ideal for ropes, mats or nets. Probably the most well-known of these is the cotton plant.
H. sexstylosa is found in lowland to lower-montane forest. It is widespread in the North Island, south from the Waitakeres, and in the South Island, from Northwest Nelson to Marlborough, Buller and Banks Peninsula. Growing to c. 8 m, with a trunk of c. 30 cm diameter, its stringy fibres form strong, lacy layers underneath its smooth, grey-brown outer bark. This layer so intrigued some early European settlers that they called the tree “thousand jacket”, whereas Māori called it “houhi ongaonga”, the houhere with leaves serrated like stinging nettle, (ongaonga). Like the bark of most trees, houhere's outer bark has many rongoā (medicinal) uses. The lacy inner bark was used for bandages, soft wrappings for babies, tīpare (headbands) and decorative poi coverings, etc.
Juvenile H. sextylosa leaves are small and rounded. Adult leaves are narrowly ovate, c. 10 x 2 cm. On a recce for TTC's botany trip in Burrows Avenue Reserve, Karori, we found a huge, ancient, multi-trunked tree with only one leaf within reach, all the rest being high in the canopy. Trying to pick it to inspect it, we found the stem was attached by a string of tough, creamy, lacy bark, thus solving the puzzle - the tree was a lacebark, possibly c. 100 hundred years old.
You have probably noticed that houhere flowers appear in autumn. They are hermaphrodite, having both male reproductive parts: stamens, and female reproductive parts: stigmas. The specific name 'sexstylosa' refers to the six styles ('specialised stalks') with their stigmas poised on top, ready to receive pollen from bees, flies or butterflies. In dense clusters, the dainty, white flowers, c. 2 cm in diameter, are non-specialised, being open in form and slightly perfumed, attracting a wide range of potential pollinators. The petals are often notched at the tip.
The unusual fruiting structures are arranged radially in circular clusters of 6 or 7, joined at the centre, green to start with, then changing to a distinct 'pinky-brown'. Each developing seed has a 'wing' or 'sail' attached, making it easier for wind or water to distribute.
Unfortunately, for many years, Wellingtonians have been planting Hoheria populnea, a northern lacebark species, in their gardens, and this city is now overrun with it - it has become weedy. Its leaves are very much broader, and more rounded than H. sexstylosai's slender ones, often with a purplish tint underneath. It has rapidly - one might even say aggressively - colonised Wellington's wild places, so please consider planting our own Wellington lacebark instead.
The main reason why we chose H. sexstylosa for this article, is that it is the only lacebark species that belongs in Wellington. Once numerous, like so many other natives, it has been wiped out by development and is now a seldom-seen refugee. Next time you're tramping the rugged hinterland of the Wellington southwest peninsula, keep your eyes peeled for the few refugia where this handsome tree survives e.g. the upper Waiariki Gorge and above the main forks in Te Kopahou Reserve. It is also a numerous component of Tararua forests - look for it there.