''Leptospermum'' is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of shrubs and small trees in the myrtle
family Myrtaceae commonly known as tea trees, although this name is sometimes also used for some species of ''
Melaleuca''. Most species are
endemic
Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, with the greatest diversity in the south of the continent, but some are
native to other parts of the world, including
New Zealand
New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
and
Southeast Asia
Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
. Leptospermums all have five conspicuous
petals and five groups of
stamen
The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the filament ...
s which alternate with the petals. There is a single
style in the centre of the flower and the fruit is a woody
capsule.
The first formal description of a leptospermum was published in 1776 by the
German botanists
Johann Reinhold Forster and his son
Johann Georg Adam Forster, but an unambiguous definition of individual species in the genus was not achieved until 1979. Leptospermums grow in a wide range of habitats but are most commonly found in moist, low-nutrient soils. They have important uses in
horticulture, in the production of honey and in
floristry.
Description
Plants in the genus ''Leptospermum'' range in size from
prostrate shrubs to small trees, and have fibrous, flaky or papery bark. The leaves are arranged alternately and are relatively small, rigid and often aromatic when crushed. The flowers may be solitary or in groups, and have
bracteoles and
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106
Etymology
The term ''sepalum'' ...
s which in most species fall off as the flower opens. There are five spreading, conspicuous petals which are white, pink or red. There are many stamens which are usually shorter than the petals and in five groups opposite the stamens, although they often appear not to be grouped. A simple style usually arises from a small depression in the ovary which has from three to five sections in most species, each section containing a few to many
ovules. The fruit is a woody capsule which opens at the top to release the seeds, although in some species this does not occur until the plant, or the part of it, dies.
Taxonomy and naming
The first formal description of a leptospermum was published by Johann Reinhold Forster and Johann Georg Adam Forster in their 1776 book, ''
Characteres Generum Plantarum''.
In 1876,
George Bentham
George Bentham (22 September 1800 – 10 September 1884) was an English botanist, described by the weed botanist Duane Isely as "the premier systematic botanist of the nineteenth century". Born into a distinguished family, he initially studie ...
described twenty species, but noted the difficulty of discriminating between species. ("The species are very difficult to discriminate.") Of the species he named, only ten remain as valid.
In 1979,
Barbara Briggs and
Laurie Johnson published a classification of the family Myrtaceae in the ''
Proceedings of the Linnean Society of New South Wales''. Although there have been revisions to their groupings, their paper allowed a systematic examination of species in the genus ''Leptospermum''.
In 1989,
Joy Thompson published a complete revision of the genus.
In 2000, O'Brien ''et al.'' published yet another revision, using
matK-based evidence to suggest that ''Leptospermum'' is
polyphyletic
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
, and should be split into persistent, Western non-persistent, and Eastern non-persistent fruiting plants, with ''Leptospermum spinescens'' as an outlier. However, neither phylogeny has been universally accepted. Current estimates recognize about ninety species of ''Leptospermum''.
The common name ''tea tree'' derives from the practice of early Australian settlers who soaked the leaves of several species in boiling water to make a
herbal tea.
The genus name (''Leptospermum'') means "slender-seeded".
Distribution and habitat
Most ''Leptospermum'' species are endemic to Australia where most are found in southern areas of the country. They are most common in moist, nutrient-poor soils although they sometimes occupy other situations. ''
Leptospermum laevigatum'' is usually found growing on beach sand and ''
L. riparium'' growing in
Tasmania
Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...
n rainforest on the edges of rivers. ''
Leptospermum amboinense'' extends from
Queensland
Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
to Southeast Asia and three species, ''
L. javanicum'', ''
L. parviflorum'' and ''
L. recurvum'' are endemic to southeast Asia. ''L. recurvum'' is only found on
Mount Kinabalu in
Sabah
Sabah () is a States and federal territories of Malaysia, state of Malaysia located in northern Borneo, in the region of East Malaysia. Sabah has land borders with the Malaysian state of Sarawak to the southwest and Indonesia's North Kalima ...
. ''
Leptospermum scoparium'' is one of the most widespread in the genus and occurs in
New South Wales
New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...
,
Victoria, Tasmania and
New Zealand
New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
, where it is one of the most widespread and important native shrub species.
Ecology
In Australia, ''Leptospermum'' species are sometimes used as food plants by the
larvae of
hepialid moth
Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s of the genus ''
Aenetus'', including ''A. lewinii'' and ''A. ligniveren''. These burrow horizontally into the trunk then vertically down.
Uses
Use in horticulture
Most ''Leptospermum'' species make desirable garden plants. The hardiest species (''L. lanigerum, L. liversidgei, L. polygalifolium, L. rupestre, L. scoparium'') are hardy to about to ; others are sensitive to frost. They tolerate most soils, but many suppliers specify
ericaceous (i.e. lime-free) compost with good drainage and full sun. Established plants are
drought tolerant. They are often found as hedge plants on the west coast of the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, and some species are popular for cultivation as
bonsai. Many
cultivars exist.
Use in floristry
These flowers are also grown in double cultivars and are used in floral designs. However, they do not last when out of water and the single flowers do not last when wired. The 'Pacific Beauty' (''Leptospermum polygalifolium'') is a useful flower to use in large church-service bowls and function arrangements, however use of ''Leptospermum'' in corporate designs is less desirable as they dry and drop when subjected to heating and air conditioning.
Honey production
The
nectar from the flowers is harvested by bees, yielding
Leptospermum honey, which is marketed as
Manuka honey.
Honey produced from Australian ''
Leptospermum polygalifolium'' is also known as ''jelly bush'' or the ''lemon-scented tea tree''.
Native honey a sweet antibacterial
''Australian Geographic'', March 3, 2011.
Species
The following is a list of species accepted by Plants of the World Online
Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew.
History
Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...
as at August 2024:
References
{{Authority control
Myrtaceae genera
Taxa named by Georg Forster
Taxa named by Johann Reinhold Forster