This article was published in The Fringe, October 2016

Peka-a-waka,  Hanging Tree Orchid

Orchids in New Zealand are numerous and widespread in many different habitats, yet they are generally unknown and unseen. They are mostly diminutive herbs that hide in swamp, tussock or forest and modestly conceal their beauty with small flowers, cryptic colouring, and shortish flowering periods while surrounded by other plants.  Perching or epiphytic orchids are the exception.

While not flamboyant, the epiphytes do draw attention to themselves with a powerful scent that radiates out from the plant during the month or so of flowering. Their flower spikes dangle tantalisingly close, but generally above nose level, so they can be difficult to smell up close.

Earina is a Pacific genus of about 10 species with two being endemic to New Zealand.

Earina mucronata is perhaps the most common and certainly it is the one that earned the genus name 'Earina' which means 'vernal' or 'springtime'. During October to December the fresh forest air is interspersed with wafts of its strong scent. Look up and around to discover the hanging bunches of white/green flowers with yellow/orange labellum. Beyond the drooping, strap-like leaves, there are clusters of densely-packed flowers, scarcely a centimetre across, on branching panicles: {Any loose, diversely branching flower cluster} about 20cm long.

Perching orchids have developed three extraordinary survival mechanisms due to the need to conserve water when you live high on the trunk of a tree, way out on its branch, or grasping the bare surface of a rock. The roots which encircle the host grab every nook and crevice to ensure the growing clump is securely attached. But to counter the extremes of such an exposed position the roots quickly develop a loose dead sheath (called a velamen) with perforations. When wet these sheaths absorb the water and retain it till the plant can store it in special cells.

When leaves of other plants open their pores during the day to absorb carbon dioxide, they lose some water vapour in the process. Epiphytic orchids keep their pores shut during the day, opening at night to absorb the CO2 and store it in special holding cells till required the next day to use in photosynthesis.

The third curious habit of epiphytic orchids is that their pollen is not granular but clumped in viscous, sticky masses designed to stick to the head of the pollinating insect when it visits the flower, and then carries it to some other flower where the pollen adheres to the stigma to complete the pollination process.

There are two other Earina species: E. aestivalis is a summer flowering form, and in autumn E. autumnalis is source of that wonderful scent as it comes into full flower.

The flower spikes of Earina mucronata are just beginning to form as I write this. By October they should be ready for the observant passer-by to enjoy.