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Monday, 18 Dec 2017

Jarrah

Elucalyptus marginata is commonly known as the Jarrah. It was once called the Swan River mahogany.  It is found growing in sand, clay, sandy loam, laterite soils in the hills and rises. A native to Western Australia and found in the South-West on the Swan Coastal Plain and in the Darling Scarp.

The scientific name of jarrah is Eucalyptus marginata. The specific name 'marginata' describes the presence of a light green vein that is present around the margin of the leaf. The leaves are usually curved, 8–13 cm long and 1.5–3 cm broad, shiny dark green above and paler below. The bark is rough and fibrous and is present throughout the year with minimal shedding. The tallest individuals are about 40m high and they occur in the jarrah forest – the biggest trees are usually termed 'king jarrahs'; these are about 2.5 – 3.0 m diameter and 35-45 m tall (look up jarrah in this website of 'champion trees' to see measurements and images http://www.nationalregisterofbigtrees.com.au.

The age of jarrah trees can also be estimated using the equation Age = 2.345 x DOB + 6.968 – where DOB is the tree diameter measured in centimetres over the bark at 1.3 m above the ground. For jarrah trees with diameters up to about 150 cm this equation is regarded as providing a reliable estimate (the growth rings of 162 trees were measured to develop this equation). However, for trees which have diameters much greater than 150 cm, these relationships probably over-estimate the age (see Whitford, K.R., 2002. Hollows in jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) trees: I. Hollow sizes trees attributes and ages. For. Ecol. Manage., 160: 201-214 for more information).

In the jarrah forest the density of jarrah trees can be high but many of these trees are small. Although small many of these trees can be old. They are growing from an old root structure called a lignotuber. This lignotuber stores nutrients but it also has many dormant growing buds so when the aboveground part is killed by, for example fire, the buds sprout and can grow to produce a tall tree if the competition from other trees is reduced. Another interesting underground feature of jarrah trees is the deep root system. There is no tap root, instead the trees grow long lateral roots in the upper soil layer and 'sinker' roots grow along these roots and penetrate the very deep soil profile. These deep roots usually reach the water table and have been found 45 m below the ground surface. These roots enable the trees to survive and grow during the dry and long summers experienced by the trees.

The flowers are white-cream/pink and flowering from June to December or January and are in clusters of between 7 and 11, Each bud has a narrow, conical bud cap and the flowers are white and bloom in spring and early summer. The leaves are long and curved, usually shiny dark green above and paler below.

 jarrah barkThe bark of the jarrah tree is long and stringy, vertically grooved and the bark sheds in long flat strips.

  marriversusjarrah nutsCompare the large marri nut to the tiny jarrah nut. This is a good way of identifying your tree.

 

 

 

 

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