Native Plant of the Month - March - Tānekaha
Tānekaha, or celery pine, as they are sometimes known, are endemic trees that naturally grow from Cape Reinga down to the top of the South Island. They have a graceful form with branches usually growing in evenly spaced whorls of five, which creates a pleasing geometry to many trees. Young tānekaha saplings often look a little like delicate christmas trees with a symmetrical triangular shape.
While tānekaha might seem common when you walk through the bush around Kaipātiki, they are not found throughout the whole of the country (and are found nowhere else in the world). Tānekaha are uncommon south of the Central Plateau and are most common in the Northland and Auckland regions, so they are a species that makes our local bush unique. Tānekaha are members of an ancient plant family called the podocarps. This family includes well-known forest giants such as kahikatea, tōtara and rimu. These trees can be thought of as the Southern Hemisphere equivalents of pines, which they are broadly related to. Podocarps mostly have leathery leaves that have a needle-like shape, have wood with resin, do not have flowers and reproduce using modified cones. These qualities don’t sound like they fit our tānekaha very well at face value, but it just goes to show how good plants are at pushing boundaries sometimes.
Tānekaha phylloclades are deceptively similar to leaves!
The common name celery pine is a description of the celery-leaf-like foliage that these trees have. However, these are not actually leaves at all! Tānekaha have phylloclades; flattened green branch stems that are adapted to act like leaves and photosynthesise. If you look carefully at a tānekaha ‘leaf’ you will see that it has clear veins and edges that step up in tiny merged fans towards the tip, forming a rough diamond shape. Each of these fanned steps or lobes that you can see is one flattened branchlet, which then merges seamlessly into the next. The scientific name for Tānekaha is Phyllocladus trichomanoides which means fern-like leaf-branch in reference to the ferny appearance of the phylloclades. Tānekaha do actually have some real leaves as well as their deceptive phylloclades, but these have been reduced over aeons to minute leaf scales that are not much bigger than eyelashes and drop off the tree very quickly.
Modified seed cones at the tips of branches look like fruit
Just like their leaves are not really leaves, tānekaha’s fruit are not technically fruit; they are actually a type of cone. Over millions of years tānekaha’s ancestors evolved their seed cones from something that originally looked more like a pine cone to the knobbly berry-like fruit we see today. Other podocarp species in New Zealand have gone through similar modifications and they also produce ‘fruit’ that look more like berries with a seed perched on their tips. This adaptation has meant that tānekaha and other podocarp species can attract birds to disperse their seeds rather than just releasing them to drift on the wind. On tānekaha these ‘fruit’ develop on the edges of a whirl of phylloclades at branch tips, looking more like a posy of flowers than a bunch of fruit.
Left: Tānekaha and kauri growing together.
Right: distinctive lichens on tānekaha trunks.
Another surprising fact about tānekaha is that these trees have friends. This isn’t just an airy-fairy good will statement. Tānekaha grow in close association with kauri wherever their ranges overlap. Areas with high densities of tānekaha in Northland and Auckland are a good indication that a site was formerly a kauri forest. Tānekaha also seem to have close relationships with particular types of lichen. Their trunks are very often horizontally banded by distinctive orange-pink lichens wherever they grow.
Tānekaha wood is strong, flexible and durable. Māori used it to make long spears, waka, walking sticks and fishing hooks, among other uses. When European colonists arrived they also used tānekaha wood to make housing, bridges, wharf pilings and railway sleepers. Tānekaha bark can be used to create a pink-red dye, which Māori made good use of on many textiles and other materials and was used to dye soldiers’ uniforms in Europe during WWI. This dye is still used by artists and others wishing to dye fabrics.