Eucalyptus gomphocephala, known as tuart, is a species of tree and is one of the six forest giants of Southwest Australia.
The trees usually grow to a height of and mostly have a single stem, but can have multiple stems under some conditions. The crown can be as wide as . It has rough box-like bark over the length of the trunk and larger branches. The glossy light-green to green adult leaves are arranged alternately and have an oval to lanceolate or falcate shape, and have a leaf blade that is long and wide. The tree flowers between January and April with white to cream inflorescences that form in the leaf axils and are not branched. The fruits that follow have an obconic to upside-down bell shape.
Tuarts were first formally described by the botanist Augustin Pyramus de Candolle in 1828. The botanist Jean-Baptiste Leschenault assembled the type collection at the Vasse River near Geographe Bay during 1802, while serving with the Baudin expedition.
The distribution range of tuart is along a narrow coastal corridor within the Swan Coastal Plain, extending inland , a continuous corridor south from Yanchep to Busselton. Tuart forest was common on the Swan coastal plain until the valuable trees were felled for export and displaced by the urban development around Perth. The wood has many uses as it is dense, hard and water resistant and resists splintering. Remnants of tuart forest occur in state reserves and parks; the tree has occasionally been introduced to other regions of Australia and overseas. Remaining trees are vulnerable to Phytophthora dieback, an often fatal disorder. It was listed as endangered by the International Union for Conservation of Nature .
Description The tree is native to the southwest of Western Australia and typically grows to a height of . The tallest known living tuart is tall and located in the Tuart Forest National Park near Ludlow. The largest tuart tree has a wood volume of . Taller trees are often found at the southern end of the trees' range, while smaller trees are found at the northern end. The crown of the tree can spread up to a width of . The habit of tuart is a tall single stemmed tree, but may form a low and multi-stemmed tree at the edge of stands in response to salinity and winds. The trees have no lignotuber but will form epicormic buds up along the stem.
Tuart has rough, box-like bark over the length of the trunk and the main branches. The bark is rough and finely fibrous. It is grey in colour and breaks into smaller flaky pieces. On large and older stems the bark tends to become tessellated. The branchlets have a circular cross-section and often have oil glands situated in the pith, although sometimes there are not many and they can be difficult to find.
Juvenile leaves are attached to the stem via a stalk and always have an opposite arrangement for the first four to eight nodes along the stem, then have an alternate arrangement. The green and discolorous juvenile leaves have an egg-shaped (ovate) to cordate shape with a length of and a width of . Adult leaves are stalked and alternate, with an oval to lanceolate or falcate shape. The leaves are slightly discolorous to concolorous, glossy, light green and thin. The leaf blade is in length and wide, and often curved. The leaves are attached to the limbs or twigs via a petiole that is typically in length. The apex of the leaf is pointed and the base tapers to the petiole. Tuart leaves have few oil glands, are densely reticulated, where the veins are packed in tightly forming a dense network in the leaf, and have side veins that branch off at an angle of over 45° to compared to the midrib.
The tree flowers between January and April and tends to have a mass flowering event every five to eight years with smaller intermittent flowering events for the years in between. White to cream flowers appear in mid-summer to mid-autumn. The inflorescences form in the leaf axils and are not branched. The peduncle has a length of with seven buds in each umbel that are attached by long pedicels. The buds have swollen caps, and are said to resemble a small ice cream cone; the caps are long. The buds are in length and have a width of with a hemispherical shaped operculum that is wider than the obconically shaped hypanthium located below. When the outer opercula is shed a scar is left. The stamen are flexed irregularly and contain an oblong anther that is attached at the rear to the filament. The anther can burst open via longitudinal slits. The style is straight and long with a blunt stigma at the tip. The style has a small cavity at the base (or locule) and holds the ovary with four vertical rows of ovules. The flowers are formed in tight clusters made up of around seven flowers. These later form into fruits with a mushroom shape containing small seeds.
The fruits are narrow and in length with a broad rim and wide. The fruits are attached to the stem via long pedicel. The fruits have an obconic to upside-down bell shape and sometimes have two longitudinal ridges that extend from the pedicel partly along the length. The fruits have a level disc that can be slightly raised or descending and have three to five valves that are partly protruding or exserted.
The seeds are usually released within a year. They are in length with an ovoid to saucer shape and a grey-brown to blackish colour. The upper side of the seed is wrinkled or marked with thin parallel streaks and sometimes has a protruding ridge around the circumference. There is a hilum scar on the rear side where it was once attached to the placenta. The seeds of this species, as for most Eucalypts, germinate quite easily and are considered one of the simplest native plants to grow from seed. Seed production has sizable variation throughout time. Seeds are usually slowly released from the canopy but many can be shed at the same time following events such as fire.
Taxonomy and naming The species was formally described by the botanist Augustin Pyramus de Candolle in the third volume of his Prodromus Systematis Naturalis Regni Vegetabilis published in 1828. The botanist Jean-Baptiste Leschenault assembled the type collection at the Vasse River near Geographe Bay during 1802, while serving with the Baudin expedition.
The isotype collected by Leschenault is held at Royal Botanic Gardens, Kew.
In 1939, William Blakely and Henry Steedman described two varieties of this species in Contributions from the New South Wales National Herbarium, but the names are listed as synonyms by the Australian Plant Census. The epithet gomphocephala is derived from gomphos, meaning 'club', and kephale, 'head',Ruthrof, K. X., Yates, C. J., & Loneragan, W. A. (2002). The biology of tuart. In: B. J. Keighhery, V. M. Longman, & W. A. Nedlands (Eds.), Tuart (Eucalyptus gomphocephala) and Tuart Communities (pp. 108–122). A Perth Branch Wildflower Society of Western Australia. describing the rounded and overlapping shape of the operculum.
The species is allied as a monophyletic arrangement within the most diverse eucalypt subgenus, Eucalyptus subgen. Symphyomyrtus, recognised as the sole species of its section.
The Noongar peoples named the tree tuart or tooart, moorun, mouarn or duart.
The tree is sometimes referred to as white gum and is the origin for the name of the Perth suburb White Gum Valley.
Distribution
The distribution range of the species is a narrow coastal corridor within the Swan Coastal Plain, extending inland , a continuous corridor south from Yanchep to Busselton. This area has been intensively cleared for changes in agricultural practices, then urbanisation, so that the numbers of tuart trees and area of forest were greatly reduced after the establishment of the Swan River Colony. Outlying patches of the tree are found to the north of Yanchep as far as Geraldton and further inland where rivers intersect the range. The species has become naturalised in other places within Western Australia. A large stand of Tuart is found adjacent to the Jurien Bay cemetery and is listed with the Heritage Council of Western Australia. This stand has scientific value and is regarded as the "northern most natural Tuart stand in the state". It also has heritage value resulting from its position along an historic stock route.
Tuarts have been introduced into parts of Europe, specifically in Spain and Italy including Sicily. The species has also been introduced into several countries in Africa, including Algeria, the Cape Provinces of South Africa, Kenya, Libya, Morocco, Tanzania, Tunisia, Zimbabwe and the Canary Islands. The tree has become naturalised in parts of southern Africa.
E.gomphocephala grows in sandy well drained soils, often over limestone, in sunny positions.
The trees are part of coastal shrubland ecosystems in areas of deep sand. They also will often be part of limited woodland communities in protected areas along the coast. Tuarts are associated with the Quindalup and Spearwood sand dune systems, both of which have calcareous soils. When they occur in woodland or open forest they are often associated with peppermint trees (Agonis flexuosa) in the understorey.
Uses As a durable hardwood, the timber is sought after for scantlings, structural timber, the construction of railway carriages and boat building. The colouring and grain pattern of the timber also make it a popular choice for furniture manufacturing. Due to over-logging, tuart is a protected tree with conditions placed on felling.
The heartwood is a pale yellow-brown colour with a fine texture and a highly interlocked grain, close and twisted, almost curled back. The green wood has a density of and an air-dried density of .
The flowers are an excellent source for the production of honey. The colour of the product is described as light and creamy and it candies quickly to become hard and dry if properly matured in the hive. In 1939, tuart was noted as a high quality source, although it was determined to be an "undependable source" thirty years later.
Essential oils are extracted from leaves and fruits of the tree. Samples of the leaves contained 0.23% essential oil and samples of the fruits contained 0.34% essential oil. The constituents of the oils collected from the leaves were 1,8-cineole (24.2%), p-cymene (20.7%), α-pinene (14.1%), β-pinene (8.12%), γ-terpinene (6.9%), methyleugenol (6.8%), α-terpineol (4.7%) and limonene (3.8%). Essential oil constituents of tuart fruits were 1,8-cineole (46.69 %), p-cymene (8.99 %), baeckeol (8.57 %), α-pinene (5.21 %), and globulol (4.25 %).
The oils all had some degree of antimicrobial activity, with the essential oil collected from the leaves generally having higher antimicrobial activity than those collected from the fruit.
Ecology Tuarts are regarded as one of the six forest giants found in Western Australia; the other trees are Corymbia calophylla (marri), Eucalyptus diversicolor (karri), Eucalyptus jacksonii (red tingle), Eucalyptus marginata (jarrah) and Eucalyptus patens (yarri). The informal definition of a giant tree is that it must be significantly larger than other species and exceed in volume.
The tree is moderately tolerant of saline soil and salt-laden winds. It is also drought and frost tolerant. Individual trees may live over four hundred years.
Experimental cultivation in the 1930s of the species identified that it was able to grow in areas of low rainfall, as little as per annum. Tuarts were introduced to France and grown extensively there by the end of the nineteenth century.
The biodiversity of tuart forest is rich, containing unique assemblages of plants, fungi and animals.