Figure 10. Melaleuca endemism. The greatest endemism occurs in the south-central coastal region
of Western Australia with some moderately strong areas of endemism in the north-western part of
the south-west. There are some lesser areas of endemism in eastern Australia.
Figure 9. Melaleuca species richness calculated using a continuous gradient from 1 to 72 species
N
0
740
1,480
2,220
2,960
Kilometres
Species richness
High : 72
Low : 1
N
0
740
1,480
2,220
2,960
Kilometres
N
Endemism
High : 9.92035
Low : 0.00518135
29
2. I
ntr
oduction to the genus
Melaleuc
a
Fenton et al. 1977), particularly in South-East Asia and
USA, can be ascribed to M. cajuputi and M. quinquen-
ervia and not M. leucadendra. Most current interest in
the species for plantation establishment is in the Mekong
Delta of Vietnam, where M. leucadendra outperforms
the indigenous M. cajuputi subsp. cumingiana on season-
ally inundated and potentially acid-sulfate sites which
are very difficult for tree establishment (Hoang Chuong
et al. 1996).
Melaleuca alternifolia is planted for the production of
essential oil in Australia—3,000 ha producing 450–500
tonnes (t) of essential oil/year—but the total area planted
and the total production worldwide is potentially twice
this from plantings outside Australia in several countries,
including China. Broombush (M. uncinata complex)
plantings in Australia for brushwood fencing and related
products exceed 1,000 ha.
There are extensive, but largely undocumented, plant-
ings of melaleucas as ornamentals, street and public park
trees, shelterbelts on farms and for land reclamation in
Australia and elsewhere.
Tolerance of difficult
conditions
As well as being tolerant of periodic (Figure 12) or
even continuous waterlogging, many of the wetland
melaleucas will also survive and grow in moderately
to highly saline soils (e.g. M. armillaris, M. bracteata,
M. cuticularis, M. decussata, M. ericifolia, M. lanceolata,
M. lateriflora, M. leucadendra, M. linariifolia, M. quinquen-
ervia, M. squarrosa, M styphelioides and the M. uncinata
Figure 11. Some of the variable habitats occupied by Melaleuca species: (A) a pure stand of tree-form
M. quinquenervia in a coastal swamp in eastern Australia; (B) the shrub M. protrusa on a dry stony hillside in
south-western Western Australia (WA); (C) shrubby M. sophisma under an overstorey of mallet in south-
western WA; and (D) trees of M. cuticularis on the edge of a wet, possibly saline area in south-western WA
A
C
B
D
30
2. I
ntr
oduction to the genus
Melaleuc
a
complex). A few melaleucas are tolerant of extremely
saline conditions (e.g. M. halmaturorum and M. thyoides).
Many of these same species are also tolerant of alkaline
soils, drought and frost (Marcar et al. 1995; Marcar and
Crawford 2004).
Melaleucas appear to employ a diverse range of
physiological strategies to adapt to difficult growing
conditions. For example, Naidu et al. (2000) found that
species with the capacity to accumulate one or, prefer-
ably, more of the methyl prolines in their leaves were
better adapted to saline and/or sodic soils than species
that accumulated only L-proline. This was the case with
M. cuticularis: Carter et al. (2006) found that the ability
of this species to tolerate saline-waterlogged conditions
was related to production of methyl proline, as well as
regulation of foliar sodium, chloride and potassium
concentrations. Ionic stress and the differential ability of
seedlings of M. leucadendra provenances to adjust for a
declining potassium concentration in leaf sap under com-
bined salt and aluminium stress was thought to be the
main cause of variation in growth of 16 M. leucadendra
provenances in a glasshouse trial (Nguyen et al. 2009).
Mensforth and Walker (1996) found that the root dynam-
ics of M. halmaturorum in response to fluctuating saline
groundwater contributed to the survival of this species in
saline swamps. Melaleuca halmaturorum accessed water
from deep in the profile in late summer when salt had
accumulated in the surface soils and used rainfall and
shallower groundwater after winter rains had replenished
the profile. The ability of this species to take up water from
saline substrates through maintenance of low leaf water
potentials was also a contributing factor (Mensforth and
Walker 1996).
Some wetland melaleucas, like the tropical M. leuca-
dendra group, develop aerial adventitious roots on their
stems and within the papery bark to the height of the
maximum water level during flooding (Figure 13). These
are dense in aerenchyma cells which have large intracel-
lular air spaces that improve internal root aeration and
gas exchange during inundation. The fine adventitious
roots on the stems of M. quinquenervia in a seasonally
inundated forest in northern Queensland, for example,
were considered an important part of the reason that tran-
spiration in this species was unaffected by inundation of
up to 24 weeks (McJannet 2008). In M. cuticularis, they
appear to contribute to this species’ enhanced tolerance to
combined salinity and waterlogging (Carter et al. 2006).
Tanaka et al. (2011) reported that seedlings of M. cajuputi
in the tropical peat swamps of southern Thailand were
able not only to survive complete submergence for 8 weeks
but also to photosynthesise and grow during this period.
This was due to the strong development in the leaves and
stems of submerged seedlings of schizogenously formed
aerenchyma which improved uptake of gases from the
water.
Many melaleucas are highly fire-tolerant during all but
the early seedling stages before a thick protective layer
of bark has formed. Fire-ravaged individuals regenerate
through stimulation of epicormic buds under the thick
bark to sprout vigorously after fire in a process called
coppicing (Figure 14). Populations may expand through
fire-induced release of seed from serotinous capsules on
the trees and stimulation of germination of seed in soil
seedbanks.
Some melaleuca species have the ability to root sucker,
and through root extension and interconnectivity form
Figure 12. Melaleuca cajuputi surviving and growing under seasonal inundation in the Mekong Delta of
Vietnam: (A) a young planting as the inundation recedes; and (B) a dense plantation nearing rotation age
A
B
2. I
ntr
oduction to the genus
Melaleuc
a
31
dense clumps of single clones. This is a common adaptive
characteristic of wetland plants subject to very difficult
conditions for survival, growth and sexual recruitment
(see review in Robinson et al. 2012). Using DNA markers,
Robinson et al. (2012) showed that the large, dome-shape
stands of M. ericifolia in Dowd Morass, Gippsland Lakes,
Victoria, were individual clones that did not intermin-
gle (phalanx growth habit) with adjacent clones. They
speculate that this is also the case with other stands of
this species in southern Australia. Melaleuca viridiflora
also forms root suckers. Crowley et al. (2009) showed that
population density of this species increased dramatically
in grasslands and grassy woodlands in northern Queens-
land in the absence of fire by recruitment of suckers to
the sapling layer.
Figure 13. Aerial adventitious roots on the stems of: (A) Melaleuca quinquenervia growing naturally in a
seasonal swamp beside the Bensbach River, Western Province, Papua New Guinea; and (B) M. leucadendra
planted in the Mekong Delta, Vietnam
A
B
2. I
ntr
oduction to the genus
Melaleuc
a
32
Figure 14. Western Australian broombush, Melaleuca concreta, coppicing after fire
33
Ethnobotanical
Some Melaleuca species were used extensively by the Aboriginal peoples of Australia
for a wide variety of cultural uses (refer to Williams 2011 for a description of 17 species
used by Aboriginal communities).
The papery bark of several, mainly tropical, melaleucas (e.g. M. argentea, M. dealbata,
M. cajuputi, M. leucadendra and M. viridiflora) had many domestic uses, including
water-repellent roofing material, raft-making, in food preparation, bandages, blankets,
baby slings, body wraps in burial ceremonies and for dresses denoting marriage, to
name but a few (Levitt 1981; Wrigley and Fagg 1993; Yunupingu et al. 1995; Blake
et al. 1998; Puruntatameri et al. 2001; Wiynjorrotj et al. 2005; Williams 2011; Wiersema
and León 2013). The leaves of species such as M. acacioides, M. argentea and M. leuca-
dendra were used as flavouring in cooking and M. argentea leaves were burnt to repel
mosquitoes. The trunks of some species (e.g. M. cajuputi, M. leucadendra and M. viridi-
flora) were used for construction of canoes and shields.
‘Bee bread’ (produced from pollen) and honey were foods
collected from native bee hives prevalent in Melaleuca
swamp forests of M. acacioides, M. lasiandra, M. leuca-
dendra, M. minutifolia, M. nervosa and M. viridiflora in
northern Australia (Williams 2011). Williams (2011) also
notes reports of early explorers (e.g. Leichhardt in 1847
and Mitchell in 1848) in northern Australia of the col-
lection by Aboriginal peoples of melaleuca honey and
melaleuca flowers (e.g. from M. saligna). The latter were
soaked in water to produce a sweet-tasting drink.
Melaleucas were an important source of dry-season
water for the nomadic Aboriginal peoples (and early
European explorers), particularly in the wet/dry tropics
of northern Australia. Bulges in the trunks of individual
trees of such species as M. argentea, M. cajuputi, M. deal-
bata, M. nervosa and M. viridiflora when undercut could
yield about a litre of brackish but nevertheless potable
water (Yunupingu et al. 1995; Puruntatameri et al. 2001;
Wiynjorrotj et al. 2005; Williams 2011).
Melaleucas played an important role in traditional
Abor iginal medicines. The leaves and inner bark of
M. argentea and others like M. cajuputi and M. leucaden-
dra were used medicinally (coughs and colds, aches and
pains, cuts and sores, ringworm, vomiting and diarrhoea
and other malaises), either directly following crushing or
burning (smoking medicine) and inhaling the odours or as
Uses
34
3. U
ses
a liniment or drink after soaking the leaves or inner bark
in water and heating (Blake 1968; Levitt 1981; Aboriginal
Communities of the Northern Territory 1993; Wrigley and
Fagg 1993; Yunupingu et al. 1995; Puruntatameri et al.
2001; Wiynjorrotj et al. 2005; Lassak and McCarthy 2011;
Williams 2011). The bark of some melaleucas was used as a
poultice on wounds and for splinting broken bones, where
the juice of the bark was said to penetrate the skin and aid
in healing (Williams 2011). The milky extract of squashed
‘bee brood’ (bee pupae and larvae) collected from native
beehives prevalent in melaleuca swamp forests was used
as a topical antiseptic for sores, tinea and eye complaints
(Williams 2011).
Ornamental, landcare,
honey, bark and wood
Ornamental and amenity–horticultural use
Melaleuca species, especially the bottlebrushes, have long
been popular garden subjects in Australia. The first Austral-
ian melaleucas to be cultivated, however, were grown in
Europe, presumably from seed taken to England in 1771
by Joseph Banks. Melaleuca armillaris, M. decora, M. erici-
folia, M. hypericifolia, M. nodosa, M. styphelioides and
M. thymifolia were in cultivation by 1793 (Elliot and Jones
1993; Wrigley and Fagg 1993). Seed and/or transplants of
the bottlebrush species M. citrina and M. linearis also were
taken to Europe in the late 1700s and these species rapidly
became popular conservatory plants. Melaleuca citrina was
in fact named and described (as Metrosideros citrina) in
1794 from material cultivated in England and M. linearis
was described in 1796 from material cultivated in Germany.
Many species (including cultivars derived from selec-
tion or from interspecific hybrids) are hardy in cultivation
in Australia (Elliot and Jones 1982, as Callistemon; Elliot
and Jones 1993; Wrigley and Fagg 1993, also as Callis-
temon; Holliday 2004; Stewart 2012, also as Callistemon).
Some tolerate moderate levels of frost and others grow well
in poorly drained soils. Because there are species of diverse
habit, flower form and colour, and substrate preference
in most of the major climatic zones within Australia, it
is possible to select a species for a specific purpose, e.g.
for a hedge, windbreak, specimen shrub or tree. Several
species have particularly attractive papery bark and are
worth cultivating for this feature. Several of the larger
shrub and tree species are ideal for amenity plantings as
street trees, screens for industrial sites, highway verges and
so on. Many of the tree species are ideal for use in parks
and large-scale landscape applications. The trees that have
colourful, nectariferous flowers (Figure 15) usually attract
nectar-feeding birds if these occur in the region.
There are surprisingly few melaleuca cultivars available
in the horticultural industry in Australia and most, if not
all, of these are selections of species. The bottlebrushes are
an exception. Barriers to successful hybridisation between
certain species apparently do not exist and, when grown in
a common garden, bird- or insect-mediated hybridisation
has resulted in the occurrence of hybrid plants. In many
cases, selections have been named and propagated com-
mercially. The following species (as Callistemon) have been
recorded as being a parent, or putatively a parent, of named
cultivars: M. citrina, M. comboynensis, M. glauca, M. pachy-
phylla, M. phoenicea, M. polandii (doubtfully this species
and more likely to have been M. hemisticta or M. pyrami-
dalis), M. recurva, M. salicina, M. subulata and M. viminalis
(Elliot and Jones 1982; Wrigley and Fagg 1993). Much more
Figure 15. Ornamental melaleucas: (A) Melaleuca ryeae, a shrub with profuse pink flowerheads; and (B)
Melaleuca cultivar ‘Harkness’
A
B
3. U
ses
35
work needs to be done as far as bottlebrush breeding is
concerned. There is considerable opportunity for breeders
to select growth and colour forms of species and cross them
with an aim of obtaining a particular combination of char-
acters. The two broad climatic zones that should be targeted
for such hybridising endeavours are the tropical–subtropi-
cal and subtemperate zones in Australia and elsewhere.
As to other species groups within the genus, it seems
there have been no hybridisation programs. The field is
open for such programs to be initiated. The pom-pom-
flowered M. scabra group is an obvious candidate as there
is much variation within this group that could be bred into
novel, improved garden plants. Although many of the spe-
cies of the M. scabra group occur on leached, sandy soils,
some of them occur on clay soils and these species may
confer some degree of soil adaptability to hybrids. Mela-
leuca nesophila, an M. scabra group species of restricted
range and habitat in the high rainfall, coastal part of south-
western Western Australia, is remarkably hardy and grows
well on heavier soils in the dry Western Slopes region of
New South Wales. Using species such as M. carrii, M. fabri,
M. hamata, M. nematophylla, M. nesophila, M. oldfieldii,
M. sapientes and M. systena—and there are many oth-
ers—it may be possible to develop hybrids of merit for
Mediterranean and dry-temperate climates.
Another group with potential as garden plants is the
M. fulgens group, and a hybridisation program involv-
ing such species as M. coccinea, M. elliptica, M. eximia,
M. fulgens, M. lateritia and M. macronychia may result in a
series of red- to orange-red-flowered, bushy plants to rival
the bottlebrushes, as the species of the M. fulgens group
also have bottlebrush inflorescences. Naturally occurring
hybridisation in Melaleuca has been reported from a wide
range of species (Craven 2006, p. 470) and it seems barriers
to hybridisation within a species group or species complex
are not absolute; in fact, where two or more species of the
same group occur in biotic sympatry, hybridisation may
be frequent.
An interesting application is the use of melaleucas as
bonsai (known as penjing in China and cay canh in Viet-
nam). Bark texture, small leaves and flowering propensity
are some of the criteria by which species are rated. Over
60 species, varieties and cultivars of Melaleuca have been
recorded by the Australian Plants as Bonsai Study Group
as being grown in bonsai within Australia (Roger Hnatiuk,
pers. comm.). Early use of melaleucas tended to mimic the
styling of classic Japanese trees but in recent years bonsai
artists are exploring the beauty of branches and crowns of
old mature trees of the species found growing in nature.
Bonsai, inspired by such forms, are beginning to be seen
in public displays (Figure 16).
Notes on species of particular, or potential, value for
ornamental and amenity–horticultural use are provided in
the ‘Species accounts’ (Chapter 7). The main impediment
to their wider use within Australia and elsewhere is the
difficulty in obtaining planting material of superior colour
and growth forms of the species, or forms from particular
soil types.
Figure 16. Examples of bonsai melaleucas: (A) Melaleuca lateritia, usually a 2–3 m tall shrub from south-
western Western Australia; and (B) M. bracteata, usually a medium-size tree up to 22 m tall from inland and
coastal northern Australia
A
B
3. U
ses
36
Land rehabilitation
Melaleuca comprises many species of trees and shrubs that
are hardy and adaptable to a wide range of habitats and
soils. They regularly occupy sites that are very challeng-
ing for tree survival and growth (Figure 17), as discussed
in other sections of this volume. Their diversity in form,
adaptability and utility sees them listed prominently
among candidate species for planting for land reclama-
tion, with natural resource benefits including mitigation
of salinity, waterlogging, and water and wind erosion.
Biodiversity improvements, carbon sequestration and
potential to increase farm income (e.g. through produc-
tion of brushwood fencing, essential oils and bioenergy)
are among other commonly stated benefits of planting
melaleucas on degraded lands.
Highly topical at present is the increasing problem of
saline landscapes in Australia and elsewhere. There are
over 4 million ha of secondary or human-induced saline
soils in Australia, in addition to 29 million ha of naturally
Figure 17. Salt-tolerant melaleucas: (A) Melaleuca halmaturorum on a saline site
in southern Australia; and (B) M. atroviridis surviving on the margin of an area
severely affected by secondary salinity in south-western Western Australia
A
B
37
3. U
ses
occurring salt-affected lands (Marcar and Crawford 2004).
The removal of native vegetation and development of annual
agricultural systems in southern Australia, leading to ris-
ing watertables carrying soil-borne salt to the surface, are
major contributors to salinisation of landscapes. Restoration
of deep-rooted perennial vegetation can make a significant
contribution to correcting this problem but it needs to be
on a large scale to control salinity (Pannell and Ewing 2004).
A range of Melaleuca species is suitably adapted to grow
on saline sites (e.g. Figure 17), ranging from moderately
(4–8 dS/m ECe) to extremely saline (>16 dS/m ECe) (Mar-
car et al. 1995; Department of Agriculture and Food Western
Australia 2004; Marcar and Crawford 2004).
Melaleuca halmaturorum is an example of a temperate
Melaleuca tree/shrub adapted to extremely saline condi-
tions, while M. leucadendra is among the tropical tree-form
melaleucas adapted to highly saline conditions. Both spe-
cies are tolerant of waterlogging. Unfortunately, few of the
presently recognised salt-tolerant melaleucas offer scope
to growers for direct financial benefits, thus large-scale
planting is not attractive. Melaleuca uncinata, one of the
source species for brushwood (see below), and its relative
M. atroviridis, are two exceptions. Melaleuca bracteata
might have potential in the future if an industry were to
develop around the production of betaines from its foliage.
Brushwood fencing and related products
Ornamental brushwood fencing comprising the grey
stems, twigs and dry foliage of the M. uncinata complex
of species (broombushes), hand-packed on wires in situ
or, in more recent times, prefabricated in panels, has been
in use in Australia for more than 80 years (McKelvie et al.
1994) (Figure 18). It represents an important market for
melaleucas, despite its small size compared with alterna-
tive fencing materials (e.g. 1% of the fencing market in
Western Australia). Other uses of brushwood include
manufacture of garden furniture, gazebos, pergolas, gates,
hanging baskets and decorative bird feeders (Robinson
and Emmott, no date). McKelvie et al. (1994) indicated
that about 600,000 bundles of brushwood (each c. 25 kg,
consisting of stems with foliage of 1.4–1.8 m in length and
7–15 mm in diameter) were used in Australia each year,
with predicted annual market growth of 5.5%.
Melaleuca uncinata is the most common broombush
used for brushwood fencing. It is widespread in southern
Australia, mainly south of the Tropic of Capricorn. Mela-
leuca uncinata is a hardy, bushy shrub to 7 m in height with
multiple long, thin, woody erect stems topped with foliage
(broom-like). It is adapted to a wide diversity of habitats
and soils, mainly in semi-arid and arid Australia (see range
given in its species description). Other broombushes in the
M. uncinata complex having potential for brushwood fenc-
ing are the Western Australian endemics M. atroviridis,
M. concreta, M. hamata and M. osullivanii (Robinson and
Emmott, no date). Melaleuca acuminata and M. hamulosa
are also worth trialling as alternative species as they have
similar physical characteristics to the traditionally used
M. uncinata (Peter White, pers. comm. 2012).
Until recent times, all harvesting of brushwood has
been in native stands and producers are licensed by the
various state governments. Overall, 50–70% of plants are
harvested manually of which 90% can be expected to cop-
pice in a typical bush operation based on a broombush
population of about 3,000 plants/ha. This yields between
3–6 t product/ ha. The interval between harvests is 10–14
years (Wrigley and Fagg 1993). Concerns about adverse
environmental effects have seen the gradual withdrawal
of public lands from resources available for harvesting and
concerns have arisen about the sustainability of brushwood
supply from native stands. The likely direct economic ben-
efits, complemented by the indirect benefits of establishing
broombush on private lands for purposes such as shelter,
salinity control, soil erosion control, biodiversity and
diversification of farm income, have led to interest among
some landholders in the drier regions of the southern
states in developing commercial plantations of broombush.
It is estimated that a total plantation area in the order of
2,000–2,500 ha would be required to fully meet demand on
a sustainable basis (Cameron 2003; AVONGRO 2007). The
total area planted is not known but about 900 ha had been
planted in the Avon catchment area of Western Australia
alone by 2007 (AVONGRO 2007).
Various landcare agencies in Western Australia, South
Australia and Victoria have published informative ‘fact
sheets’ on growing broombush by either direct seeding or
planting tube stock and readers interested in this topic are
directed to these for detailed information (e.g. Bulman et
al. 1998; Cameron 2003; Robinson and Emmott, no date).
Until recently, broombush was regarded as being a single
species, M. uncinata. It is now known that there are several
species involved (Craven et al. 2004), a number of which
are suitable for brushwood production as mentioned above.
Honey
Most melaleucas do not provide major honey crops. Clem-
son (1985), however, pointed out that many species assist
indirectly with honey production by providing nectar and
pollen, especially nectar, in sufficient quantities to stimu-
late brood-rearing and sometimes for use as stores. In this
way, colonies are maintained and built up for subsequent
major honey flows in other taxa.
Those which are important honey producers include
the broad-leaved melaleucas. Melaleuca quinquenervia is
a major source of honey in Australia and Florida (Blake
and Roff 1972; Robinson 1981; Clemson 1985; Geary 1988)
and similarly M. cajuputi in northern Australia and Viet-
nam (Brock 1988; Mulder 1992). Melaleuca leucadendra
is also said to be an important source of honey in its area
3. U
ses
38
of natural occurrence (Roff 1966; Anderson 1993). The
honeys from these species are variously described as light
to dark amber in colour, with strong flavour and odour
and of low density so they granulate readily. Their pollens
are universally described as being a good source of protein
utilised by bees in building up colonies.
Bark
The bark of Melaleuca species is still used today in the con-
struction of traditional houses in Papua New Guinea. It is
used to line fernery baskets, for making bark paintings and
the cork from the bark has been used in infants’ pillows
and mattresses (Bootle 1983). The bark of M. cajuputi is
used in parts of Malaysia as a luting material in boatbuild-
ing (Lum 1994; Lim and Midon 2001).
Wood
Fuelwood
There is little reported on the fuelwood value of individual
species in the genus Melaleuca. Apart from the state-
ment in Maiden (1889) that M. linariifolia wood made
Figure 18. Facets of the brushwood fencing industry: (A) the multistemmed habit of species in the broombush
complex (this is Melaleuca stereophloia); (B) a native broombush (M. uncinata) population; (C) broombush
bundles in the field ready for transport; (D) transporting the bundles to market; (E) constructing a brushwood
fence in situ; and (F) a typical brushwood fence
A
C
E
B
D
F
39
3. U
ses
a first-class fuel, most published reports of the fuelwood
value of melaleucas refer to the larger-growing species
in the tropical broad-leaved M. leucadendra group. The
wood of M. quinquenervia, for example, is reported to be
an excellent fuel and converts into good-quality charcoal.
The reported calorific values for the wood and bark of this
species are around 18,400 and 25,800 kJ/kg (4,400 and
6,160 kcal/kg), respectively (Wang et al. 1981), but there
is great variability in these values between trees (Wang
and Littell 1983). The uniquely high heat of combustion
of M. quinquenervia bark (equivalent to some coals) is
due to the presence of a great amount of fatty substances
in the bark (Wang et al. 1982). Keating and Bolza (1982)
rated M. cajuputi and M. leucadendra as good fuelwoods,
although often difficult to split because of interlocking
grain. Gough et al. (1989) reported that the light wood of
M. leucadendra was quick to ignite, with sooty acrid smoke
initially produced from the burning bark.
Posts, poles, stakes and sticks
The stems of the larger melaleucas like M. cajuputi, M. leu-
cadendra, M. quinquenervia and many other species were
regularly used in the round or roughly fashioned for use
as posts, poles, piles, mine timbers and general construc-
tion materials (e.g. rafters for huts, fencing rails) in the
early days of settlement in Australia (Maiden 1889). Posts
were said to be durable in contact with fresh or salt water
(e.g. M. cajuputi, Blake 1968), although Cherrier (1981)
reported that durability of untreated M. quinquenervia
posts in the ground was high for 1 year but declined
thereafter, and replacement was necessary after about 3
years. In present-day Vietnam, there is widespread use
of the roundwood of the indigenous M. cajuputi and the
introduced M. leucadendra for piles, poles and general
construction materials (Figure 19).
A specialised industry exists in Western Australia to
supply sticks for use in the lobster-fishing and vegetable-
growing industries (Peter White, pers. comm. 2012).
Although other myrtaceous species may be used, such as
Kunzea sp., sticks derived from natural stands of M. viminea
are preferred due to their greater durability. It is believed that
lobsters enter pots made from natural materials more readily
than they do pots made from synthetic substances. In recent
years, about 1.2 million M. viminea sticks/year have been
used in making lobster pots. Additionally, large numbers of
M. viminea stakes are used each year in the vegetable-grow-
ing areas of the Gascoyne region for supporting climbing
beans. Presently, these markets are supplied from natural
stands but it may be that, in the future, the supply of sticks
and stakes could be augmented from plantation sources.
Sawn wood
The wood of the broad-leaved paperbarks M. cajuputi,
M. leucadendra, M. quinquenervia and M. viridiflora has
yellowish sapwood, merging gradually into pinkish-brown/
red/grey heartwood. It has a high silica content (0.2–1.0%)
which blunts saws and planes. It is hard, heavy and of
moderate strength, with wood from native trees giving a
green density of c. 1,070 kg/m3 and an air-dry density of
c. 750–800 kg/m3 (Keating and Bolza 1982; Bootle 1983).
Florida-grown wood of M. quinquenervia has a basic
specific gravity of 0.49, a density of 1,070 kg/m3 (green),
640 kg/m3 (air-dry) and 620 kg/m3 (oven-dry) (Huffman
1981). Collapse is slight, with shrinkage about 3.5% radial
and 7% tangential (Bootle 1983). Sawn timber tends to
check and warp but, if carefully seasoned, it is suitable
for general construction and flooring. Boards are difficult
to plane and mortice due to interlocking grain but glue
well and are good for joinery. Boat knees can be cut from
branches using their natural shape.
Figure 19. Production and marketing Melaleuca poles and piles in Long An province, Vietnam: (A) harvesting
and loading poles onto a barge for transport to market; and (B) stacks of melaleuca poles at a roadside market
A
B
40
3. U
ses
Woodchips
Vietnam is the main producer of Melaleuca woodchips for
use in fibreboard production. In 2010, 100,000 t (bone-
dry) of Melaleuca woodchips were exported from Vietnam
to China, presumably for this purpose. Presently, there are
well-advanced plans to establish a medium-density fibre-
board (MDF) plant in the Mekong Delta of Vietnam to
utilise the Melaleuca resource directly (Stephen Midgley,
pers. comm. 2012).
The ‘kraft’ pulping potentials of 2-year-old paperbark
wood from Vietnamese plantations were reported by Chen
and Su (1998, as M. leucadendron). The low pulp yield and
high chemical consumption were unfavourable pulping
characteristics but the strength index was adequate and
bleachability excellent. The authors indicated that older
trees might have better pulp qualities.
Extractives
Organic chemicals produced and stored naturally in
plant tissues are numerous and chemically complex. By
definition, extractives are the organic chemicals that can
be removed from plant tissues by the action of water,
including steam, other inert solvents such as alcohol and
by mechanically crushing the source materials. The types
of extractive from selected Melaleuca species that are of
economic importance or have commercial potential fall
into two classes: non-volatile (e.g. betaines) extractives and
volatile (foliar essential oils).
Non-volatile extractives
The foliage of a range of Melaleuca species produces com-
mercial levels (>2% fresh weight) of betaine (Naidu and
Cameron 1999). Betaines are non-volatile, water-soluble
compounds and comprise three methylated prolines:
N-methylproline, trans-4-hydroxy-N-methylproline and
trans-4-hydroxy-N,N-dimethylproline. They are osmo-
protectants against stress (e.g. unfavourable temperatures,
drought, soil salinity) in tolerant plants and on application
(foliar and seed treatment) to stress-susceptible plants can
create acquired tolerance. Naidu (2003) believes that the
use of betaines to increase stress tolerance in Australian
agricultural crops would stabilise and even increase the
national income from agriculture.
Glycine betaine, a by-product of the sugar-beet indus-
try, is currently sourced from Finland and a worldwide
shortage is predicted for this solute. Australian melaleucas
are a good alternative source of osmoprotectants. Naidu
(2003) found that M. bracteata, which accumulates a pro-
line analogue, trans-4-hydroxy-N-methyl proline, had the
greatest potential of the melaleucas tested for commercial
development, because of its adaptability, vigorous growth
and high yields. Despite this potential, there have been no
recent reports of further development of this opportunity.
Research has also shown Melaleuca bark and leaves to
be a rich source of phenolic extractives (tannins) (Huffman
1981; Hussein et al. 2007) but no commercial exploitation
of phenolics from melaleucas for uses such as wood adhe-
sives, leather tanning and as antimicrobial agents has been
reported.
Novel flavonoids have been identified in the leaf waxes,
seeds and honey of several Melaleuca species (e.g. Courtney
et al. 1983; Wollenweber et al. 2000; El-Toumy et al. 2001;
Yao et al. 2004; Yoshimura et al. 2008). Similarly, various trit-
erpenes, some previously undescribed, have been extracted
from the leaves, bark, wood and seed of various melaleucas
(e.g. Ahmad et al. 1997; Lee and Chang 1999; Vieira et al.
2004; Bar et al. 2008). Habila et al. (2010), for example,
have reported the extraction of a triterpene, betulinic acid,
from the wood of M. bracteata. They tested this compound,
which they state is known for its anti-HIV and cytotoxic
activity against malignant versus non-malignant cancer cell
lines, and against a number of pathogenic organisms from
the genera Trichophyton, Candida and Microsporum. They
found that it had ‘great potential’ as an antifungal drug.
Foliar essential oils
An essential oil is the (usually) hydrophobic liquid contain-
ing the volatile compounds that are found in the oil glands
or trichomes of a plant. These glands are usually associ-
ated with the leaves, although bark, wood or roots of plants
may also contain essential oil. The oil is usually obtained
by steam distillation, although the expressed oil (as in the
case of citrus peel) can also be used. Essential oils are usu-
ally associated with species in the families Myrtaceae and
Rutaceae, although they do occur in some other families.
Commercially important oils
Relatively few Melaleuca species have essential oils of com-
mercial interest. One of the first species to be exploited
commercially for its foliar oil was M. cajuputi subsp. caju-
puti in the Maluku archipelago of Indonesia, probably in
the first part of the eighteenth century. It was one of the
first products imported to Europe from South-East Asia
by the Dutch (Gildemeister and Hoffman 1961, cited in
Lowry 1973), because of its reputation as a panacea in the
treatment of all kinds of diseases. Cajuput oil is produced
currently in South-East Asian countries including Indo-
nesia, Cambodia and Vietnam and annual production
potentially exceeds 600 t (Doran 1999a, b). This oil is rich in
1,8-cineole (typically 40–60% of total oil) (Doran 1999a, b;
Pujiarti et al. 2011), as is medicinal Eucalyptus oil but at
slightly higher proportions (70% or more). Cajuput oil
acts as a mild antiseptic and is especially useful for treat-
ing respiratory ailments, but also finds use in a wide
range of personal-care (e.g. ointments and liniments) and
3. U
ses
41
household products (Doran 1999a, b; Lassak and McCa-
rthy 2011). Niaouli oil from the 1,8-cineole-rich form of
M. quinquenervia (40–80% 1,8-cineole) was, until recently,
produced in Madagascar from plantations yielding 1.5–2.0 t
of oil/year. This oil was used for similar purposes to cajuput
oil (Ramanoelina et al. 2008; Lassak and McCarthy 2011).
Production of niaouli oil in New Caledonia from natural
stands of M. quinquenervia (Trilles et al. 1999, 2006) has
now also ceased after many years of exploitation, although
there is new interest in producing this oil type in Vietnam
(Le Dinh Kha, pers. comm. 2012).
The basis for the commercial interest in, and develop-
ment of, the Australian tea tree oil industry—utilising
mainly plantations of M. alternifolia established in north-
ern New South Wales and northern Queensland and
plantings made outside Australia—can be traced back
to the 1920s. It was then that the medicinal properties
of the oil were first studied and reported (Penfold and
Grant 1925). The terpinen-4-ol-rich oil produced from
M. alternifolia was found to be a powerful antimicro-
bial agent. It has demonstrated its ability to serve as an
antiseptic, antifungal, antiviral, antibacterial and anti-
inflammatory agent in multiple studies and is relatively safe
for topical applications (Southwell and Lowe 1999; RIRDC
2007; Lassak and McCarthy 2011). It is incorporated into
many personal-care and household products and is seeing
increasing use in products designed for agricultural and
animal-husbandry purposes (Figure 20). Annual produc-
tion in Australia of Australian tea tree oil is estimated to be
in the order of 400–500 t, worth approximately A$15–20
million at the farm gate.
The three abovementioned species/chemotypes provide
the bulk of the commercial production of essential oils
from the genus at present. In addition, there is sporadic
interest in the following oils.
Linalool-rich oil is sourced from specific provenances
of M. ericifolia. Linalool, with its fruity notes, is of value to
the flavour and fragrance industries and, although it can be
produced synthetically, there remains a market in aroma-
therapy where natural linalool is preferred (Coppen 1995).
E-nerolidol-rich oil can be extracted from the appro-
priate chemotype of M. quinquenervia. This compound,
presently sourced from a diminishing world supply of
cabreuva oil (Erich Lassak, pers. comm. 2007), has an
established market in perfumery where it is used as a base
note in many delicate, flowery odour complexes (Bauer
et al. 1997). Melaleuca quinquenervia was shown to yield
and coppice well in plantations in northern Queensland
(Doran et al. 2007) before the recent arrival of myrtle rust
to Australia (see Chapter 5).
E-methyl cinnamate has been derived from a northern
Queensland form of M. viridiflora (Hellyer and Lassak
1968; Brophy and Doran 1996). Methyl cinnamate is a
colourless, crystalline solid with a fruity, sweet-balsamic
Figure 20. A sample of the many products that utilise Australian tea tree oil
3. U
ses
42
odour and its uses include as a flavour enhancer and in
perfumery (Bauer et al. 1997). A small market exists for
the natural product, but it can be produced artificially at
relatively little cost and there is strong competition from
other natural sources.
Platyphyllol, a b-triketone, is found in M. cajuputi. It
has been identified as having ultraviolet-blocking attributes
and insecticidal properties but it is not being produced
commercially at this time (Yaacob et al. 1989; Brophy and
Doran 1996; Doran 1999a, b).
Citral-rich oil is extracted from M. teretifolia (Southwell
et al. 2003, 2005). A small production of this oil has com-
menced from natural stands and plantations in Western
Australia. The producer claims the oil has perfumery and
therapeutic properties.
An objective of work undertaken for this book was, if
possible, to identify other species/chemotypes of melaleuca
with commercial potential. The results of this work are
summarised in the ‘Species accounts’ (Chapter 7) and in
Appendix 1, which provides a quick reference to the oil
type(s) present in individual species.
Inter- and intra-specific variation
Essential oils from a plant species are not necessarily
chemically uniform. There can be, and usually is, variation
in the compounds contained in the oil and their relative
percentages. For this reason, chemists studying the essen-
tial oils of plants try to examine samples of the oils from
a number of plants, preferably from many different sites.
Variation in the essential oils may be continuous over a
geographical region, or it can be quite discrete. This latter
occurrence leads to the finding of different chemotypes of
the plant, i.e. plants which, though morphologically the
same, produce different essential oils. It is possible, because
of inadequate sampling, to find two different oil composi-
tions within a species (i.e. two chemotypes) when, in fact,
they just represent the extremes of a continuous variation.
Examples of both types of variation as they apply to the
main (M. quinquenervia, M. alternifolia and M. cajuputi)
and one minor (M. ericifolia) commercial oil-producing
species are discussed below. The possible presence within
a species of these types of variation should be borne in
mind when interpreting the results given in the fol-
lowing sections.
The essential oil of M. ericifolia has been studied for over
50 years. A 2004 study examined its essential oil content
over its natural geographical range, which extends from
coastal regions near Newcastle, New South Wales, in the
north to Tasmania in the south (Brophy and Doran 2004).
The study looked particularly at the amount of 1,8-cin-
eole and linalool in the oils and the results are shown in
Figure 21. Generally, the amount of 1,8-cineole increases
from Newcastle southwards to Tasmania, and the amount
of linalool decreases concomitantly. As the essential oil of
M. ericifolia is important because of its linalool content, it
is important to source the oil from plants in the north of its
range. But there is a continuous variation in oil contents so,
in this case, it is not correct to refer to a cineole chemotype
or a linalool chemotype.
Melaleuca quinquenervia, in contrast, is a species known
to contain chemotypes. There are two distinct chemotypes
of this species; chemotype I contains E-nerolidol as the
major component (in amounts of up to 95%) of the oil,
while chemotype II contains major amounts of either
1,8-cineole or viridiflorol (or both), as well as lesser
amounts of other terpenes. There is no plant producing
an oil containing significant amounts of all three oils
(E-nerolidol, 1,8-cineole and viridiflorol). Viridiflorol
production is catalysed by terpene synthase enzymes. The
genes coding for these enzymes are present in the genome
of all plants of the species, but are expressed only in the vir-
idiflorol chemotype (Padovan et al. 2010). The Australian
distribution of the two chemotypes has been mapped and
is shown in Figure 22 (Ireland et al. 2002). The chemotype
containing major amounts of 1,8-cineole is the basis of the
niaouli oil industry.
Melaleuca alternifolia exists in several chemical forms
(chemotypes), although among them there are only three
principal forms (Butcher et al. 1994; Homer et al. 2000).
These three chemotypes contain terpinen-4-ol (up to 50%),
the chemotype on which the tea tree oil industry is based,
1,8-cineole (up to 60%) and terpinolene (up to 50%). Pro-
duction of the oils of these three chemotypes is controlled
by three different enzymes (Keszei et al. 2010a, b). The
1,8-cineole chemotype is not used commercially, and the
oil presents a similar oil profile to a eucalyptus or niaouli
oil. This particular type of oil is very common in species of
Melaleuca (see Appendix 1). The terpinolene chemotype
found in M. alternifolia (Southwell et al. 1992) also occurs
in M. trichostachya (Brophy 1999).
Melaleuca cajuputi subsp. cajuputi, the basis of the
cajuput oil industry in South-East Asia, contains up to
approximately 60% of 1,8-cineole, together with lesser
amounts (approximately 10%) of limonene, a-terpineol
and viridiflorene, and spathulenol (up to 30% in some
cases). There are, however, a few isolated cases of this spe-
cies, from northern Western Australia, producing an oil
containing large amounts of E-nerolidol and virtually no
1,8-cineole (J.J. Brophy et al., unpublished data).
Species by oil type
With 290 species in the genus Melaleuca, it is not sur-
prising that their leaf oils have much variation, resulting
in many different types of oils. In this short section, we
will review this variation and show what a wide range of
chemicals is contained in Melaleuca leaf oils. The full data
from the analyses are provided on the internet, accessible
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