Manuka on Spheroids
As the Kererū (breathlessly) flies, 100km north of Dargaville metropolis lies Mahinepua Peninsula. The peninsula snakes away in an easterly direction to meet the Pacific Ocean, before breaking up into Motuekaiti and Motueka Islands. It is relatively quick walking along the small headland courtesy of an updated track the Department of Conservation have installed to protect a complex of archaeological sites.
One of these traces of occupation is a narrow depression running perpendicular to meet the adjacent shores of a small sandy isthmus. On first glance it may appear as a well worn track, but its straightness and V-shape owes to the profile of waka being dragged from bay to bay. Understandably, this was an easy shortcut to the alternative of paddling around the peninsula and a convenient place to leave waka away from the influence of the tides. There are nearly one hundred other discovered archaeological features throughout this headland including terraces, middens, stone walls, mounds and drains. It was clearly a place of strategic advantage and provided decent conditions for gardening. With a somewhat less interesting gardening history, is Motuekaiti Island. This island, a mere 200m to the north is bearing the hangover from a colonial retreat. In a Governor Grey-esque fashion, Norfolk pines, Phoenix palms and bamboo pepper its surface. Hinting at the previous location of the homestead and garden on the shore.
Since 1978, Mahinepua has been in scenic reserve, grazing has stopped and native plants have been regenerating. Some of the flora is a remnant of the regions coastal vegetation and is distinct in having both pōhutukawa-mamaku forest and mānuka-mamangi scrubland. Under the shelter of lichen draped pōhutukawa boughs, glossy coastal plants of shifting greens like Pseudopanax lessonii, Geniostoma rupestre var. ligustrifolium and Astelia banksii take hold.
The scrubland is a low, lime carpet of Hebe ligustrifolia, Leucopogon fasiculatus and Coprosma arborea rolling away under mānuka with a prostrate growth habit. Terry Hatch was responsible for bringing this form of mānuka into cultivation and is now sold at nurseries as Leptospermum ‘Mahinepua’. Walking through these fields of scrub, there are hints of the interesting geology of the area. Areas of erosion reveal cream-yellow clays underlying most of the vegetation. At the most easterly end is an area of bright red soil reminiscent of the serpentine geology of North Cape. Basalt lava flows are associated with the Bay of Islands volcanic field which occurred 9.5-1.3 myr. The soil at the tip of Mahinepua is of volcanic origin, having developed in basalt scoria and ash from these ancient eruptions. It has a high content of iron oxide which gives it this red colouration. The strange orange-red spherical rocks are bound by columnar joints from this basalt flow. Over time they have been chemically weathered by iron as it percolates through the soil, this phenomena is known as spheroidal weathering. Alongside these spheres, mānuka and pōhutukawa cling precariously to crumbly red clay above the Pacific Ocean.
