Species

Leptospermum scoparium var. scoparium

Etymology

Leptospermum: slender seed
scoparium: like a broom

Common Name(s)

Manuka, kahikatoa

Current Conservation Status

2018 - At Risk - Declining

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Previous Conservation Status

2012 - Not Threatened
2009 - Not Threatened
2004 - Not Threatened

Authority

Leptospermum scoparium J.R.Forst. et G.Forst. var. scoparium

Family

Myrtaceae

Brief Description

Common small prickly shrub or small tree with flaky bark and more or less hairy new growth and bearing masses of oval pointed leaves and white or pinkish red-centred flowers. Leaves hard, 5-20mm long by 1-8mm wide, prickly to grasp. Flowers to 25mm wide. Fruit a dry 5-7mm wide capsule.

Flora Category

Vascular - Native

Structural Class

Dicotyledonous Trees & Shrubs

Synonyms

None - a myriad of varieties have been proposed none of which has been strictly synonymised within L. scoparium. Allan (1961) discusses some of these, and accepted one (var. incanum). A modern taxonomic assessment of Leptospermum scoparium is urgently needed.

Distribution

Indigenous to New Zealand and Australia. Most Australian forms of L. scoparium do not match the range seen in New Zealand. However, plants from Tasmania are very similar to, if not identical with some South Island forms, differing in having a lignotuber, wider leaf bases, and longer, more pungent leaf apices. Leptospermum scoparium was also collected once from Rarotonga by Thomas Cheeseman in the 1800s. It has not been found there since. It's biostatus on that island is unclear.

Habitat

Abundant from coastal situations to low alpine habitats.

Features

Decumbent shrub, subshrub, shrub, or small tree up to 5 m in height and in decumbent forms 2-4 m across. Bark light grey to charcoal grey, peeling in long papery flakes, these curling with age. Wood red. Branches numerous erect, spreading or decumbent, arising from base, sometimes sprouting adventitious roots and/or layering on contact with soil. Young branches, young leaves and flower buds densely to sparingly clad in long silky, white hairs. Leaves leathery, pale to dark green, glabrescent to glabrous, linear-filiform, narrowly lanceolate, lanceolate, oblanceolate, to elliptic or obovate (5-)10-15(-20) x 1-2-5(-8) mm, invariably apex drawn out into a long stiff, pungent point, midrib usaully distinct sometimes obscure, leaf margin finely crenate, veins simple, scarcely branched. Flowers solitary in leaf axils, (8-)10-20(-25) mm diam. Receptacle dark red, crimson or pink. Petals white, sometimes flushed pink or dark red. Stamens numerous.

Similar Taxa

With the exception of L. scoparium var. incanum a broad circumscription of the the New Zealand forms of manuka (L. scoparium) has been adopted. In this sense, manuka could only be confused with kanuka (Kunzea spp.) and Great Barrier Island kanuka (Kunzea sinclairii), fromwhich it can be easily distinguished by the hard, persistent, circular, nut-like fruits, with non persistent sepals, sharp-tipped minutely denticulate leaves, and flowers which appear to be solitary.

Flowering

Throughout the year

Flower Colours

Red / Pink,White

Fruiting

The capsules are long persistent so invariably mature plants possess at least some capsules.

Propagation Technique

Very easy from fresh seed. Seed must be sown fresh, even if left for a few weeks before sowing viability can drop, especially if seed is allowed to dry out. Difficult from cuttings.

Threats

Although widespread and common, some stands are at risk from clearance for farmland or through felling for firewood. The recent (2017) arrival of myrtle rust (Austropuccinia psidii) may pose a more serious threat to Leptospermum (see below).

Chromosome No.

2n = 22

Endemic Taxon

No

Endemic Genus

No

Endemic Family

No

Where To Buy

Commonly cultivated. However many garden forms are horticultural selections based on crosses between L. scoparium var. incanum and white or red-flowered L. scoparium var. scoparium. Some seem to represent natural variations, others may stem for deliberate crosses with Australian forms of L. scoparium and allied species. Recently a number of Australian Leptospermum have been introduced into New Zealand, and these have been deliberately crossed with manuka.

Myrtle Rust Threat

Myrtle rust (Austropuccinia psidii) was first detected in New Zealand in 2017. As there is as yet no known effective treatment for that rust. Overseas indications are that this rust is having a serious impact on Myrtaceae worldwide, including causing such severe declines in some that extinction of some species and genera seems inevitable. As such the New Zealand Threat Listing Panel elected to list all indigenous Myrtaceae using the 'Precautionary Principle' as 'Threatened' (de Lange et al. 2018). Hopefully this assessment will be proved wrong. As of 2018 there have been very few occurrences of myrtle rust on Leptospermum. However, the rust is still in its early establishment phase. Australian experience suggests it may take 10 or more years to truly establish which New Zealand Myrtaceae will be most affected.

Fact Sheet Citation

Please cite as:  de Lange, P.J. (Year at time of Access): Leptospermum scoparium var. scoparium a Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. http://www.nzpcn.org.nz/flora_details.aspx?ID=2302  (Date website was queried)

Attribution

Fact Sheet prepared for NZPCN by P.J. de Lange 1 February 2004. Description by P.J. de Lange.

References and further reading

de Lange, P.J.; Rolfe, J.R.; Barkla, J.W.; Courtney, S.P.; Champion, P.D.; Perrie, L.R.; Beadel, S.M.; Ford, K.A.; Breitwieser, I.; Schönberger, I.; Hindmarsh-Walls, R.; Heenan, P.B.; Ladley, K. 2018: Conservation status of New Zealand indigenous vascular plants. 2017. New Zealand Threat Classification Series 22: 1–82.

Gardner, R. 2002. Notes towards an excursion Flora .Manuka Leptospermum scoparium myrtaceae. Auckland Botanical Society Journal, 57: 147-149 

 

This page last updated on 22 Dec 2018