This article was published in The Fringe, April 2015
Mangemange or Bushman's mattress.
Found throughout the same region as kauri, there is one fern that is quite distinctive and unlikely to be confused with other native ferns. In fact it is most like some of the native vines such as Parsonsia or Clematis, with a tangle of wiry, scrambling, leafless stems terminating in a dense head of foliage, generally well above a viewer's head.
The strange thing is that the trunk or rhizome of the fern is a relatively obscure and comparatively short growth at ground-level. From it the fern's fronds evolve and grow, scrambling and twisting until they have latched onto a twig, branch, or stem of a sturdy neighbour which they use as the support structure for their entangled mesh of fern stipes (the base portion, or stalk of a frond before the leaf proper develops). Once up into the open, usually 3 metres or so above the ground, the fronds produce the sterile green pinnae of the leaf blade (or lamina) which is a work of art in its delicacy and geometry as it unfolds. With mathematical precision the pinnae divide and divide again with the secondary pinnae spreading out like the fingers of a hand. The resultant structure looks incredibly delicate yet is amazingly resilient with the newly unfolding pinnae searching for a twig to twine around and anchor the new growth. In this way the stipes continue to grow to an indefinite length creating impenetrable curtains of fine, tough stems, which, when cut down (not recommended) apparently make a springy mattress, as used by bushmen if the need arose.
The pinnae endings develop into either sterile or fertile growth. The former are flat, smooth blades 10 cm long, while the latter are about 1 cm long, wrinkled, fan shaped segments ending in spore-bearing structures which release clouds of yellow dust when ripe.
Mangemange is the only New Zealand species in the genus, but about 30 or 40 related species occur throughout the tropics and some such as mangemange grow into the temperate zone. Many have been declared noxious weeds overseas, where they have been taken out of their natural environment and introduced into other parts of the world without their natural predators. This is a good example of why we should not be exporting our native plants overseas, nor wilfully introducing new ones into New Zealand. While mangemange is certainly annoying if you trip on it while tramping through the bush, it is a suitable plant for the garden in a sheltered shady spot where it has some levels of foliage to give it a hand up to the canopy. It is not a demanding plant and once established will grow moderately fast and not require much maintenance other than redirecting errant fronds.
Enjoy it for its exclusivity as a northern New Zealand endemic deserving of a place in both the Waitakere Ranges and in your garden.