Botany

Trees of Australia Acacia Acuminata



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There are over 900 acacia species native to Australia and Acacia acuminata is one of these. It has the local name of ‘jam tree’, as the smell of freshly cut wood is reminiscent of raspberry jam.

The acacias are a large group of shrubs and trees that belong to the subfamily Mimosoideae. They are found throughout the world. Around 2005, ‘Acacia’ was retained for the species found in Australia with ‘Vachellia’ and “Senegalia’ applying to most of the species found outside of Australia.

 The jam tree is one of the taller wattle species, commonly found on loamy soils, with an understorey of native grasses. It is often found in connection with York gums and she-oaks. Endemic to Western Australia, it is found throughout the south-west. It is common in the wheatbelt and extends into the semi-arid interior. Under ideal conditions it may reach ten metres but under normal field conditions it grows to around five metres in height.

Like most acacias, the ‘leaves’ are actually phyllodes (modified leaf stalks). The elliptical phyllodes are bright green, about 10cm long and 2mm wide. The phyllodes finish in a long point. (Acuminatus means ‘pointed’ or ‘elongated’.) The flowers appear in tight, lemon-yellow, cylindrical clusters. Pods appear after flowering and are light brown, flat and about 10cms long and 5mm wide.

The timber is popular for wood turning. The colour is a rich brown with a yellow core and, when turned, produces striking items. However, its main function, during the early days of Australia’s settlement, was as fence posts, referred to as jam posts. The jam was popular for fencing as it was relatively accessible and resistant to white ants. It is a hard and durable timber with a close grain.

There are several subspecies and some variations within these.

The so-called ‘typical’ variant is a tall shrub with few branches at ground level and linear to narrowly elliptical phyllodes. The seeds are 2 to 3mm long and a glossy black.

Another variant, more common in the northern regions of its range, has larger seeds of 4 to 5mm long and 3 to 3.5mm thick. The pods are rounded over the seeds.

The main variation between the types is in the breadth of the phyllodes. The typical variant has the broadest while the phyllodes on trees further towards the northern limits become progressively narrower. It can be very difficult to distinguish between the variants with atypical specimens occurring out of the ‘normal’ range.

Nowadays, jam trees are planted as host plants for sandalwood trees. They have a high tolerance to frost and are moderately salt tolerant. They need at least 250mm average annual rainfall.

As a host plant for sandalwood, the jam tree has gained a new prominence. With an increasing interest in commercially produced quandong seeds (a relative of the sandalwood – they are both root parasites), the jam tree looks like broadening its career as a host plant.


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