Manuka & Kanuka: Identify these two species

Posted on July 30, 2014

Although Manuka (kahikatoa) and Kanuka have a superficial similarity and are collectively known as ‘tea trees’, they are genetically very distinct from each other.

Manuka (Leptospermum scoparium), called ‘tea tree’ by Captain Cook, is a rather variable plant ranging from flat creeping forms and small shrubs to tall trees (up to 4m tall).

Although variable, all the forms of this species are unified by their sharp-tipped leaves, large, solitary white or pink-flushed flowers, with distinctive short, dark red stamens, and persistent greyish-white nut-like capsules. Manuka plants are sometimes covered with sooty mould, a black fungus that feeds on the honeydew produced by scale insects.

Kanuka (Kunzea ericoides), although superficially similar to Manuka, is a rather different plant. In its typical form it can grow into a tree up to 15m tall. The trunk and branches are usually clad in long, leathery strips of bark, rather than the short, papery, rather flaky brown bark typical of the tree forms of Manuka. Kanuka leaves lack the sharp tip of Manuka. The flowers of Kanuka are usually solitary but occur in clusters. The capsules of Manuka remain on the lower branches of the trees for several years while Kanuka sheds its capsules within one year. Manuka capsules are approximately 8–10mm in diameter while Kanuka are 4–5mm in diameter.

Recent research has confirmed that Kanuka is endemic to New Zealand.

Where are they found?

Manuka is common throughout the North, South and Stewart Islands in lowland to low alpine regions up to 1800 metres above sea level. It can be found in many different habitats including wetlands, river gravels and dry hillsides. When mature, it is very tolerant of drought, waterlogging, strong winds and frost and it can grow at less fertile, colder, wetter and more acidic sites than Kanuka.

With the notable exception of Taranaki, Kanuka is common throughout lowland and mountain scrub and along forest margins of the North and South Islands from the Three Kings Islands to about Kawarau Gorge and Dunedin in Otago. It is not found naturally south of there. The species has a wide range of tolerances and has been found growing around active geothermal systems. It can be found from sea level to 1800 metres. It grows well on all soil types except water-logged soils, and is tolerant of wind, drought and frost.

Facts

  • Early settlers battled hard to clear their land and regarded Manuka and Kanuka as invasive shrubs that undid all of their hard work. Today however, these plants can act as an important tool for re-vegetating bare, eroded slopes. By creating shade and shelter from the wind, they provide an excellent nursery for other, slower growing native plants. Then, as these other plants get taller and overtop them, the Manuka and Kanuka die away as a result of being shaded.
  • Unlike many other native plants, Manuka and Kanuka are not usually eaten by browsing animals like sheep, cattle and goats. This is another reason that these plants are useful in restoration projects.
  • The hard, red wood of Manuka was widely used by Maori for everything from paddles, weapons, spade blades, bird spears and mauls to house building. The bark was used for making water containers and the inner bark as a waterproof layer for roofing.
  • Captain Cook and early settlers called Manuka ‘tea tree’ because they used the green leaves to make a substitute for tea. They also brewed twigs from this plant with rimu to make beer.
  • Manuka flowers smell very sweet and they provide an important source of nectar for honey bees, native solitary bees, flies, moths, beetles and geckos.

Did you know?

Chemical tests have shown that Manuka nectar, and honey derived from it, contains powerful anti-bacterial and anti-inflammatory enzymes, that help fight bacterial infections. Manuka oil is now sold in New Zealand and overseas in various cosmetics and health care products.

Threats

Both these plants are still widespread and common throughout New Zealand. However, they are often considered unwanted scrub and are burned or poisoned in order to clear land for pasture. Removing Kanuka and Manuka often eliminates the potential for further forest regeneration.

A taxonomic revision of Kanuka nearing completion, suggests that the New Zealand Kunzea ericoides is divisible into 11 entities. One of these, currently known as Kunzea ericoides var. linearis is inadequately protected and is seriously threatened in large parts of its range by inbreeding with other Kanuka varieties, habitat loss and the widespread use of it for firewood.

One other entity, currently known as K. ericoides var.microflora is endemic to geothermal systems of the Taupo volcanic zone, while a third, as yet unnamed species is confined to a remnant dune system near Whakatane.

Manuka (Leptospermum scoparium) is more variable but it has been little studied from a taxonomic viewpoint. Unlike Kanuka, New Zealands Manuka is also present in Tasmania. Further research may find that New Zealand Manuka should be divided into a number of species or sub-species.

For further information please click on http://www.doc.govt.nz/conservation/native-plants/manuka-kahikatoa-and-kanuka/