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Plant of the Month - April: Kahikatea/white pine



April

Kahikatea / White Pine

Dacrycarpus dacrydioides



Kahikatea are the gentle giants and guardians of our wetlands. They are Aotearoa’s tallest indigenous tree species, growing to a height of up to 65m tall, and are also the oldest member of the whole podocarp family, having diverged over 160 million years ago. These towering trees were once very common in lowland, wetland and river-flat areas across the motu but today are less common in northern regions due to logging for their wood and the clearing and draining of wetlands for use as farms. The greatest concentration of these trees can now be found on the west coast of the south island, sometimes (but rarely) up to 700m in altitude. To find the largest kahikatea, and thus the largest native tree in Aotearoa, we recommend that you visit Kaniwhaniwha near Mount Pirongia.



Blue-grey new growth of Kahikatea


Kahikatea are identifiable by their pale-grey, ‘hammer-marked’ bark and straight bare trunk. Their leaves as juveniles are flatly and alternately arranged either side of the stem (comparable to those of miro) and often have a copper-like hue, whereas adults tend to have small, pointy, rounded, and overlapping leaves arranged in a rimu-like tendril. Kahikatea are dioecious, meaning that trees are either male or female. Both male and female cones are terminal (at the end of shoots) and male cones produce pale yellow pollen, as shown below. Trees are relatively slow growing and of narrow conical form, reaching 40-60 metres over 600 years. Kahikatea trees tend to have buttress roots that support them on the soft and unstable wet ground that they love and stabilise and protect the earth around them from erosion. What an amazing tree!



Kahikatea seedling


Pollen cones on male kahikatea tree


The name Dacrycarpus aptly means ‘tear shaped fruit’, after the droopy fruit of trees in this genus. Dacrycarpus is a small genus with one species in Aotearoa and eight species found in Fiji, Southeast Asia and China. Kahikatea fruit are an important food source for native birds such as kererū, tūī, korimako and kākā in the autumn, and an example of their sometimes very extensive fruiting habit is shown in the picture below. In the fruiting season, the canopies and forest floor near kahikatea often turn delightfully karaka (orange). To find kahikatea in Kaipātiki, the best reserves are Smith’s Bush and Stancich Reserve.


Unfortunately kahikatea fruit are also eaten by possums and rat species, directly in competition with the native birds that need them most. These berries can bolster their populations leading into winter, so it’s very important to set traps and bait around kahikatea during their fruiting season to lessen their impact on our native flora and fauna.


Kahikatea 'fruit'


Kahikatea once prominently grew in large monospecific groves of flat, fertile land in the North Island - prime areas for farming and settlement. The ‘solution’ for early European developers was to log these extensive kahikatea stands, create dairy farms in their place, and mill the odourless and soft wood of kahikatea into butter boxes, which would preserve butter without tainting it on its long journey to the United Kingdom. This occurred for much of the late 1800s and early 1900s. The soft sapwood of kahikatea rots easily in water or damp environments, so structural uses of the wood were limited. Read more about the demise of kahikatea here.



Men weighing butter boxes, 1930’s. Credit to Envirohistory NZ.


Māori use kahikatea extensively for food, building materials, and rongoā, or medicine. Its wood can be infused in water to treat stomach and bladder problems, while the bark can be used to numb the mouth. The bitter-sweet resin is also used as chewing gum. The fleshy aril or koroī (the orange, fleshy part of the fruit) has also been an important food source for Māori and was served in large amounts at feasts. Burnt kahikatea heartwood is also used as the pigment for traditional tā moko. As the fruit grow on the ends of shoots and branches at the top of the trees’ canopy, historically, expert-tree climbers were called upon to harvest the fruit for feasts and this would sometimes result in fatalities. Kahikatea wood was also favoured for making bird spears.



Young kahikatea in Kauri Glen Reserve


We’d love to increase the number of kahikatea in Kaipātiki as this region has many areas that would once have been perfect for their waterlogged-loving ways! Think of Wairau Valley and the many streams and estuary catchments - these would likely have been full of grand mature stands of kahikatea freely regenerating. We recommend a walk through Smith’s bush to see some examples of remnant and regenerating kahikatea forest.


Whilst kahikatea is not an ideal tree for smaller gardens, it’s wonderful for larger sections - especially those with wetter, fertile soils or near waterways (but they can also be happy in drier sites with good rainfall). Kahikatea is ideal for supporting unstable or eroding soils and tends to be very easy to establish and grow. It’s an awesome tree for attracting birds from nearby forests to increase biodiversity without planting a wide selection of plant species. Just be mindful that they can grow to upwards of 50m tall and 2m wide - not the best tree for a pot, or right by a fence or deck!


Contact us at enquiries@pfk.org.nz if you have any questions about kahikatea, the suitability of your backyard for planting them, or for tools and resources to control weeds and animal pests in your backyard.



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