Manuka & Kanuka

These two New Zealand natives have suffered since European settlers came into the country and cleared bush for farmland.

They are first native plants to grow after clearing - farmers refer to them as 'scrub' and often burn or spray them back to create or retain pasture and can look on it as a pest.

Manuka image: (C) wikipedia user gerald.w

In reality what these scrubby plants try to do is reclaim bush areas, the first plants to regenerate on cleared ground, creating a nursery for the taller trees that will slowly overtake it.

While many people confuse these trees they are actually separate members of the same family as eucalypts, rich in leaf oils. While a lot of firewood is labeled manuka it may be kanuka as it can be hard to tell the difference. Manuka is believed to be our most common shrub but kanuka, being much taller, is probably more likely to be cut for firewood.

It is easy to tell the difference between kanuka and manuka when the plants are young – grab a branch at its base and pull your hand along it. Juvenile kanuka has silky leaves, manuka leaves feel sharp and rough. As they get older manuka is prone to manuka blight so develops bark that looks sooty, whereas kanuka does not.

Both plants are excellent choices for revegetating bare sites that suffer from erosion. They are easily propagated and enjoy direct sunlight. As they grow they create habitat and protection for birds, who then bring in seed of other, larger trees and so create a nursery for developing native bush.

Kanuka (image copyright: DOC)
Kunzea ericoides
Also known as tea tree or scrub
Adult height: Up to 25m high
Description: Very erect trees, papery bark and small leaves, grows clusters of white flowers from September to February
Tolerant of wind, drought, frost and almost every soil type (it doesn’t like being water-logged), this hardy tree can be harvested for oil or eventually cut down to use as a great firewood. It is the perfect nursery tree to protect other natives, forming clumps where seedlings can be in shade and gain protection from the elements. Kanuka likes warmer temperatures on a dry, semi-fertile site and isn’t found in South Westland, Fiordland, Southland or Stewart Island.

Manuka
Leptospermum scoparium
Also known as tea tree or scrub
Adult height: Up to 10m high
Description: Short, scrubby tree with white flowers three times the size of kanuka.
Known as the number one pioneer tree, most manuka is short and scrubby but it is a rare specimen in that it supports both main types of myccorhizal fungi, which trees use to graduate to more efficient complete multi-canopy ecosystems. It also makes a perfect canopy for young native seedlings to grow through. More susceptible to the scale insect which tends to kill young plants. Manuka is found almost everywhere, from lowlands up to sub-alpine levels in a variety of habitats. It was used by maori and early settlers to make a strong black tea with a wonderful aroma. Honey made by bees using pollen from manuka has also been found to have some of the tree’s amazing anti-bacterial properties and is highly valued.

Essential oils
Both kanuka and manuka make a valuable essential oil and are extracted using steam distillation from the leaves, to create two very different types of oil. There are also regional variations so you end up with chemically different products.

It is much easier to extract kanuka oil, taking only 40 minutes at most to extract the oil from the plant – manuka can take up to 6 hours. Kanuka was originally used by maori for pain relief, skin diseases and to help people sleep. The essential oil has anti-bacterial, anti-fungal and anti-inflammatory properties and was used against internal worms.

Manuka oil is used as an antiseptic and has anti bacterial properties and is active against pathological bacteria like Staphylococcus, Listeria, and Streptococcus, and against some fungi.

Both types of oil can be harvested from the wild sustainably with a plant taking about 3-5 years to regrow. Researchers at Crop and Food believe it would probably be better long term to plant crops and harvest mechanically.

More reading
Manuka/kahikato & kanuka - Department of Conservation
Cropping manuka for honey - Taranaki Daily News

Nadene Hall
NZ Lifestyle Block magazine