thumb|Tea tree, 'Ruby Glow' cultivar, [[Cambria, California.]]

thumb|'Wiri Donna' cultivar, [[Auckland Botanic Gardens|upright ]]

thumb|'Burgundy Queen' cultivar, [[MHNT|upright ]]

Mānuka (; Leptospermum scoparium) is a species of flowering plant in the myrtle family Myrtaceae, native to New Zealand (including the Chatham Islands) and south-east Australia. Bees produce mānuka honey from its nectar.

The Latin specific epithet scoparium means 'like broom', referring to Northern Hemisphere genera such as Genista and Cytisus which it superficially resembles, but to which it is only distantly related.

Description

Mānuka is a prolific shrub-type tree and is often one of the first species to regenerate on cleared land. It is typically a shrub growing to tall, but can grow into a moderately sized tree, up to or so in height. It is evergreen, with dense branching and small leaves long and broad, with a short spine tip. The flowers are white, occasionally pink, – rarely up to – in diameter, with five petals. The wood is tough and hard.

Mānuka is often confused with the related species kānuka (Kunzea ericoides) – the easiest way to tell the difference between the two species in the field is to feel their foliage – mānuka leaves are prickly, while kānuka leaves are soft. Alternatively, the seed capsules of mānuka are large ( in diameter) and often remain on the plant year round, whereas the seed capsules of kānuka are much smaller ( in diameter) and are not present for much of the year.

History and habitat

Evidence suggests that Leptospermum scoparium originated in Australia before the onset of the Miocene aridity, and moved as a result of long-distance dispersal events to New Zealand from eastern Australia sometime during the last 20 million years. Cyclones and other wind activity are most likely responsible for transporting seeds long distances. It has been postulated that on arrival in New Zealand, L. scoparium became established in limited edaphically suitable areas until the arrival of the Polynesian people, whose fire and forest-clearing brought about the low-nutrient-status soils for which it was preadapted in its homeland.

Native bush regeneration

Mānuka can quickly colonise areas of disturbed land, and can create environments where other native species can establish more successfully. Because of this, mānuka is often utilised by conservation projects in New Zealand. The scale insect, Eriococcus orariensis, is a sap-sucking insect that feeds on L. scoparium.

Pollinators

Pollinators that visit Leptospermum scoparium include Melangyna novaezelandiae, Hylaeus, and honeybees.

Continued evolution

Leptospermum scoparium is in the process of evolutionary differentiation as a result of its isolation from fellow members of the Leptospermum genus. New studies demonstrate a loss of lignotubers among populations of Leptospermum scoparium located in relatively fire-free zones of New Zealand's South Island, while Australian and Tasmanian populations retain their lignotubers along with stronger manifestations of serotiny. Recently, however, new research suggests that plant-to-plant variation far outstrips the variation seen between geographically isolated manuka sites, at least with regard to nectar chemistry.

Names

The name mānuka is Māori; it comes from Proto-Polynesian *nukanuka or *nuka which refers to Decaspermum fruticosum due to its similar small white flowers; it is a doublet of the aforementioned kānuka (referring to not only Kunzea ericoides but also Kunzea robusta).

Other common names for this species are New Zealand teatree, just tea tree, ', and mānuka myrtle. Captain Cook assigned the name tea tree as his men would use the leaves to make a 'tea' drink. "Jelly bush" is also used in Australia to describe similar honey from Leptospermum polygalifolium.

Cultivation

Numerous cultivars have been developed for garden use, of which the following have gained the Royal Horticultural Society's Award of Garden Merit:

  • (Nanum Group) 'Kiwi'
  • 'Nichollsii Nanum'
  • 'Red Damask'
  • 'Silver Sheen'

Many more cultivars are available in New Zealand but often the plant performs better in cultivation overseas. This is because in its homeland it is subject to attack by scale insects that secrete a honeydew on which grows a sooty mould that eventually debilitates the plant. Because of this, attempts have been made, with limited commercial success, to cross the showy New Zealand cultivars with mould-resistant Australian Leptospermum species.

Uses

thumb|upright|Mānuka (Leptospermum scoparium) essential oil in a clear glass vial

In traditional Māori culture, mānuka was used for a wide variety of uses, including as a building material, for items such as combs, paddles and digging sticks, to construct eel weirs, for weaponry, and to construct pallisade walls of pā. The plant also had uses in traditional rongoā medicine, with infusions being made from leaves, or by collecting mānuka gum.

Mānuka leaves have been used as a flavouring agent in craft beers and tonics.

See also

  • Manuka, Australian Capital Territory, which, although it is pronounced differently, was indirectly named after the New Zealand name for the tree.
  • Tea plants (Camellia sinensis) are also grown commercially in New Zealand.

References

  • New Zealand Plant Conservation Network – Leptospermum scoparium var. scoparium
  • A review of Leptospermum scoparium (Myrtaceae) in New Zealand