Leptospermum scoparium
(manuka)

Preferred Common Name

• manuka

Other Scientific Names

• Leptospermum floribundum
• Leptospermum scoparium var. eximum B.L. Burtt (1940)
• Leptospermum scoparium var. forsteri S. Schauer (1841)
• Leptospermum scoparium var. incanum Cockayne (1917)
• Leptospermum scoparium var. linifolium (Sol. ex Aiton) R.Br. ex Aiton (1811)
• Leptospermum scoparium var. martinii hort.
• Leptospermum scoparium var. myrtifolium (Sol. ex Aiton) R.Br. ex Aiton (1811)
• Leptospermum scoparium var. nichollii Turrill (1912)
• Leptospermum scoparium var. nichollsii Dorr. Sm.
• Leptospermum scoparium var. parvum Kirk (1899)
• Leptospermum scoparium var. prostratum Kirk (1899)
• Leptospermum scoparium var. rotundifolium Maiden & Betche
• Leptospermum scoparium var. scoparium J.R. Forst. & G. Forst. (1776)

International Common Names

• English: broom tea; manuka; manuka (Australia); tea tree
• French: leptosperme à balais

Local Common Names

• English: Australian tea tree; New Zealand tea bush; New Zealand tea tree; red tea tree
• Australia: broom tea tree
• Brazil: árvore-chá; érica; falsa-érica; leptospermo
• Germany: Manukastrauch, Roter; Südsee-Myrte, Besenartige
• New Zealand: kahikatoa; katoa; manuka; pata; rauiri; rauwiri; tea tree
• South Africa: manuka myrtle; manukamirt
• Sweden: rosenmyrten
• UK/England and Wales: tea tree
• USA: broom tea tree

EPPO code

• LEKSC (Leptospermum scoparium)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Myrtales
•                         Family: Lithomyrtus
•                             Genus: Leptospermum
•                                 Species: Leptospermum scoparium

Stephens et al. (2005) reported the following on this species taxonomy: 

“A comprehensive taxonomic revision of the genus Leptospermum listed 79 species (Thompson, 1989), which has been increased to 83 with later additions (Dawson, 1997). L. scoparium is one of 13 species included in the Leptospermum myrtifolium subgroup, the defining characteristics of which are deciduous sepals and persistent strongly wooded fruit-valves (Thompson, 1989). The Australian species within this sub-group are extremely difficult to define; L. continentale and L. rotundifolium were recently elevated by Thompson (1989) from L. scoparium varieties to species rank. The species L. juniperinum and L. squarrosum have both been recorded as varieties of L. scoparium (Thompson, 1989), and the endemic Tasmanian L. scoparium var. eximium could be considered to warrant species status, displaying lignotuber development which is not found in New Zealand’s L. scoparium (Bond et al., 2004).”

Dawson (2009) discussed the many forms found in cultivation including red-flowered, pink-flowered, double-flowered, prostrate and dwarf forms, and concluded that the pool of variation for L. scoparium is by no means exhausted.

Webb et al. (1988) describe L. scoparium as the following:

“Shrub of diverse habit, or tree up to c. 4 m high. Bark shedding in long strips. Branchlets and young leaves clothed in silky hairs. Leaves subsessile, ± 4-12-(20) × 1-4 mm, of 2 main forms on different plants, narrow-lanceolate or ovate, coriaceous, rigid, acute, pungent, erect to patent. Flowers axillary, or occasionally terminal on branchlets, ± sessile, usually solitary. Hypanthium broadly turbinate; calyx lobes ± triangular, caducous. Petals c. 6 mm long, ± suborbicular, usually white, rarely pink, patent. Stamens c. 20, < to slightly > style; filaments much more slender than style. Ovary apex glabrous. Capsule 5-celled, 3-7 × 4-10 mm, woody, long-persistent, distinctly exserted beyond receptacle rim”.  

Although native to New Zealand, Stephens et al. (2005) suggest that manuka spread extensively within the country only after the opening up of newly disturbed areas as a result of human settlement. In Hawaii, according to Starr et al. (2003), manuka and other species of Leptospermum were planted for forestry, slope stabilisation or landscaping and later naturalised and spread, sometimes forming dense stands. Manuka has also been planted as an ornamental in South Africa, and is proposed as a declared plant, but more information is required before it can be listed (SABONET, 2002).

Soil drainage

• free
• impeded
• seasonally waterlogged

Soil reaction

• acid
• very acid

Soil texture

• heavy
• light
• medium

Natural Dispersal (Non-Biotic)

The species seeds prolifically and the seed is light and readily transported by wind. Release of seeds from the capsules is expedited by burning.

Accidental Introduction

This form of introduction is unlikely to occur.

Intentional Introduction

The species has been deliberately introduced and transported to other countries, primarily as an ornamental but also for forestry and soil conservation purposes.

In the past in New Zealand, hill country farmers (and to some extent governments) have spent much time and effort in controlling manuka, which tends to spring up in large numbers when land is cleared for pastoral agriculture. Besides the lost production from its direct effects on pasture, costs have included hand slashing, mechanised clearing and herbicides used in attempts to maintain pastures clear of manuka and other species like gorse (Ulex europaeus) and broom (Cytisus scoparius). However, because of the increasing economic value of manuka honey, large blocks of land in New Zealand are currently being planted in manuka. Consequently, this plant is no longer seen as a weed causing negative economic impacts in New Zealand but one that can be financially viable. Furthermore, research funding is now being directed towards growing profitable strains of the plant rather than limiting its growth (Harrington and Gregory, 2009; Massey University, 2012).  

L. scoparium plays an integral part in many of New Zealand’s natural ecosystems, and is now considered valuable for its role in succession and slope stabilisation.

In Hawaii, Starr et al. (2003) reported: “L. laevigatum and L. scoparium were both planted on Lana'i during forestry efforts in part to stabilize the eroding soils. According to Robert Hobdy (DLNRDOFAW) (pers. comm.), both species stayed put for a long time then suddenly began to spread, with L. scoparium being the more aggressive of the two. With thick shrubby growth, not much else can grow beneath Leptospermum infestations. Seeds are light and numerous, being spread on the wind.”

Impact on Habitats

Not relevant in New Zealand, and no information from elsewhere.

Impact on Biodiversity

Not relevant in New Zealand, and no specific information from elsewhere.

In the past, many hill country farmers have despaired at the lack of control of manuka.

Recently in New Zealand, disputes over the ownership of manuka honey produced from wild manuka have resulted in some bee-keepers sabotaging hives of opposition keepers in attempts to get the manuka honey for themselves (K.C. Harrington, Massey University, New Zealand, personal communication, 2013).     

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Fast growing
• Has high reproductive potential
• Gregarious
• Has high genetic variability

• Ecosystem change/ habitat alteration
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture

• Competition - monopolizing resources
• Competition - shading
• Herbivory/grazing/browsing
• Rapid growth

• Highly likely to be transported internationally deliberately
• Difficult/costly to control

Economic Value

Firewood

New Zealand Maori used L. scoparium as firewood, among other uses, and it continues to be highly valued as firewood. A modern website says ‘Manuka firewood is a native hardwood and burns extremely hot and slow, making it the best available. Suitable for open fires, pizza ovens and log fires (Waikato Firewood Company, 2008).

Essential Oils

Stephens et al. (2005) reviewed the status of essential oils in New Zealand’s L. scoparium populations. These have received considerable attention in the past 20 years. Analysis of commercially available oils showed 100 components of which 51 were identified and made up about 95% of the content. Triketones, sesquiterpene hydrocarbons and monoterpene hydrocarbons are the three main components, and the proportions of these three groups vary considerably between populations in different parts of the country. Manuka oil is readily available from many different sources, and is touted as being useful for the complexion, for aromatherapy, as an antibiotic, and for many medical conditions, especially those affecting the skin.

Manuka Honey

L. scoparium is a major source of honey harvested by the introduced honeybee (Apis mellifera) and the production of manuka honey has become a major industry both in New Zealand and elsewhere. Although many honey types have antibacterial properties because of the presence of hydrogen peroxide, only manuka honey has a high level of non-peroxide anti-bacterial activity (Stephens et al. 2005). This non-peroxide antibacterial factor has been named Unique Manuka Factor (UMF). Manuka honey is now used in many medical products in many countries.

Amenity Plant

L. scoparium is used in amenity plantings along roadsides in New Zealand, and the many attractive cultivars are extensively used as garden ornamentals in many countries, including Britain, the United States, New Zealand, Australia and South Africa.

Social Benefit

According to Stephens et al. (2005), New Zealand Maori traditionally used L. scoparium for food, medicine and timber. A sugary gum sometimes found on the branches was given to infants or used to treat coughs in adults. Infusions of leaves or bark were used for various ailments, and the timber was used for implements. L. scoparium is named tea-tree because Captain James Cook used its leaves for brewing tea when he first arrived in New Zealand in 1769.

Environmental Services

The species germinates and grows quickly, making it ideal as a soil stabiliser. Under natural conditions in New Zealand, dense stands eventually thin and the species is replaced by taller-growing forest species. In Hawaii, L. scoparium was introduced partly for this reason, but is now regarded as invasive (Starr et al., 2003). However, Harris (2004) adds that “While they are classed as an "alien invasive pest plant" they have provided some benefits by stabilising ridge tops that have eroded following grazing by goats.”