| Leptospermum | |
|---|---|
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| Leptospermum squarrosum | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Myrtales |
| Family: | Myrtaceae |
| Tribe: | Leptospermeae |
| Genus: | Leptospermum J.R.Forster &G.Forster[1] |
| Synonyms[1] | |
Leptospermum/ˌlɛptəˈspɜːrməm,-toʊ-/[2][3] is agenus of shrubs and small trees in the myrtlefamilyMyrtaceae commonly known astea trees, although this name is sometimes also used for some species ofMelaleuca. Most species areendemic toAustralia, with the greatest diversity in the south of the continent, but some arenative to other parts of the world, includingNew Zealand andSoutheast Asia. Leptospermums all have five conspicuouspetals and five groups ofstamens which alternate with the petals. There is a singlestyle in the centre of the flower and the fruit is a woodycapsule.
The first formal description of a leptospermum was published in 1776 by theGerman botanistsJohann Reinhold Forster and his sonJohann 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 inhorticulture, in the production of honey and infloristry.
Plants in the genusLeptospermum range in size fromprostrate 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 havebracteoles andsepals 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 manyovules. 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.[4][5][6]
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.[7][8] In 1876,George Bentham 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.[4][9]
In 1979,Barbara Briggs andLaurie Johnson published a classification of the family Myrtaceae in theProceedings 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 genusLeptospermum.[10] In 1989,Joy Thompson published a complete revision of the genus.[11] In 2000, O'Brienet al. published yet another revision, usingmatK-based evidence to suggest thatLeptospermum ispolyphyletic, and should be split into persistent, Western non-persistent, and Eastern non-persistent fruiting plants, withLeptospermum spinescens as an outlier.[12] However, neither phylogeny has been universally accepted.[13] Current estimates recognize about ninety species ofLeptospermum.[4]
The common nametea tree derives from the practice of early Australian settlers who soaked the leaves of several species in boiling water to make aherbal tea.[14] The genus name (Leptospermum) means "slender-seeded".[15]
MostLeptospermum 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 andL. riparium growing inTasmanian rainforest on the edges of rivers.Leptospermum amboinense extends fromQueensland to Southeast Asia and three species,L. javanicum,L. parviflorum andL. recurvum are endemic to southeast Asia.L. recurvum is only found onMount Kinabalu inSabah.Leptospermum scoparium is one of the most widespread in the genus and occurs inNew South Wales,Victoria, Tasmania andNew Zealand, where it is one of the most widespread and important native shrub species.[4][11][16][17]
In Australia,Leptospermum species are sometimes used as food plants by thelarvae ofhepialidmoths of the genusAenetus, includingA. lewinii andA. ligniveren. These burrow horizontally into the trunk then vertically down.
MostLeptospermum species make desirable garden plants. The hardiest species (L. lanigerum, L. liversidgei, L. polygalifolium, L. rupestre, L. scoparium) are hardy to about −8 °C (18 °F) to −10 °C (14 °F); others are sensitive to frost. They tolerate most soils, but many suppliers specifyericaceous (i.e. lime-free) compost with good drainage and full sun. Established plants aredrought tolerant. They are often found as hedge plants on the west coast of theUnited States, and some species are popular for cultivation asbonsai. Manycultivars exist.
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 ofLeptospermum in corporate designs is less desirable as they dry and drop when subjected to heating and air conditioning.
Thenectar from the flowers is harvested by bees, yieldingLeptospermum honey, which is marketed asManuka honey.[18] Honey produced from AustralianLeptospermum polygalifolium is also known asjelly bush or thelemon-scented tea tree.[19]
The following is a list of species accepted byPlants of the World Online as at August 2024:[20]
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