One of the many fascinating species associated with kauri trees are kauri orchids, which are found under kauri trees.
There are two species of kauri orchid within the genus Pterostylis (greenhood orchids): Pterostylis agathicola and Pterostylis brumalis.
The kauri orchid is a terrestrial, perennial, deciduous herb with a long underground tuber. They only grow in kauri forests, often in leaf litter, and close to large kauri trees. They are endemic to the North Island of New Zealand and there are two different forms: flowering and non-flowering.
The flowering form is a single green and transparent white flower on a leafed spike. When not in flower, they appear as a rosette of leaves on the ground. Pterostylis agathicola flowers between July and October, while P. brumalis flowers from April.
Greenhood orchids are distinguished from other orchids by their unusual pointed, hooded flower structures and their pollination mechanism. Interestingly, they are almost always pollinated by tiny flies or mosquitos. The insect is drawn by a scent and enters the flower. Upon entering the orchid, the labellem of the flower moves forward, trapping the insect inside. In the struggle to exit, the insect pollinates the flower with pollen from a previously visited flower and collects new pollen from the greenhood to take on to the next flower.
The fruit of the greenhood orchid is a dehiscent (something that splits or bursts open) capsule containing around 500 tiny seeds, which are spread on the wind. These seeds find their way to the shadows of mature kauri trees to start the lifecycle anew.
Kauri trees are considered ecosystem engineers due to their effect on soil composition; the highly acidic leaf litter creates a nutrient-poor, acidic soil type called podsol. There are a number of plant species, such as kauri orchids, that are specially adapted to this environment, and therefore are only found near kauri trees.
Less than one per cent of historic kauri forest remains— and it is under threat from dieback. Kauri dieback threatens not only the trees themselves, but the entire ecosystem of associated flora and fauna (such as kauri orchids) that they support. You can help protect kauri orchids by following kauri dieback protocols as well as participating in predator control.
Fun etymology of Pterostylis agathicola and Pterostylis brumalis:
Pterostylis — derived from the Greek words pteron ‘wing’ and stylos ‘column’
agathi – from kauri genus ‘agatha’
cola - latin word meaning ‘inhabit’
brumalis – latin ‘bruma’ meaning shortest day or winter solstice, referring to the winter flowering of this orchid.
Photo credit: Christopher Stephens