Linda GreenBoab trees of the Kimberley

The 4,000km drive from Perth to Darwin undertaken by my husband and me last year took us through the heart of Australia’s boab country, the Kimberley region. And what magnificent trees they are.

Boabs south of Wyndham

Boabs south of Wyndham

Each tree seems to have its own unique character with its life story etched into the distinctive swollen trunk. The pale, smooth trunks of the nippers taper like a candle up to a flame of branches above while the huge, gnarled trunks of the grand oldies are dimpled, pitted and scarred, a testament to the long lives they have lived. It is believed that some of the trees are an amazing 3,000 years old, quite an achievement considering the harsh environment in which they live.

Boabs near water

Boabs near water

In the Kimberley there are only two seasons – the Wet and the Dry. For months during the Wet the average daily temperature is above 38°C and floods and thunderstorms are common and cyclones are not uncommon.

During the Dry, the weather is predictably dry for many months and bush fires can burn uncontrolled for weeks. Water taken up by the trees in the Wet is stored in the trunks until it is needed to sustain the trees during the dry.

Shady Boab between Derby and Fitzroy Crossing

Shady Boab between Derby and Fitzroy Crossing

Another adaptation that helps boabs survive is that they are deciduous during the Dry so moisture isn’t lost due to transpiration. The Dry season starts in the Kimberley in April and as we were there in June the boabs were in various stages of shedding their leaves, some were completely bare while others still had a handsome canopy which provided a lovely dense shade.

Boab Prison tree canopy

Boab Prison tree canopy

The compound leaves are divided into between 5 and 9 leaflets, arranged spirally.

Lightning strikes ignite many bushfires and routinely strike boabs. Presumably the water stored in the trunk offers some protection against the heat of bushfires. However if the bark is burnt it peels off to reveal a fresh layer underneath. Unfortunately they have no protection (as far as I know) against lightning and are usually killed after being struck.

Scorched Boabs at Telegraph Hill

Scorched Boabs at Telegraph Hill

Boab Prison Tree near Derby

Boab Prison Tree near Derby

Over time some of the soft spongy trunk tissue of older trees dies causing the trunk to become hollow. The size of the hollow can be substantial and some that we saw could easily provide shelter for 3 or 4 people. In the 1890s some of these hollows were used to hold prisoners. The Boab Prison tree near Derby wasn’t actually a prison but was used as a staging post when prisoners were being transported to Derby. Its girth is impressive at around 14m and it is said to be about 1500 years old.

Boab Prison Tree trunk

Boab Prison Tree trunk

According to signage at the site, indigenous people believe that the Derby Boab Prison Tree and certain other boabs in the area are imbued with mystical powers. Sadly these trees have not always been treated respectfully as attested by their use as lockups and being vandalised with carved graffiti.

Boab festooned with seed pods

Boab festooned with seed pods

Boab in the dust at sunset

Boab in the dust at sunset

Unfortunately we were visiting at the wrong time of the year to see the flowers which are described as large, white and fragrant with many protruding stamens however there were still nuts adorning some of the trees. The nuts are round or oval shaped, up to about the size of an adult hand and contain seeds embedded in white pith which is very rich in vitamins and minerals.

Boab street trees in Derby

Boab street trees in Derby

Boabs can be propagated by seed and have been successfully transplanted, most famously by the Botanic Gardens and Parks Authority when they relocated a 750 year old tree from the Kimberley to King’s Park in Perth. They are grown in gardens across the north and are used as street trees in various towns including Derby and Kununurra.

Boabs growing in the red earth of El Questro station

Boabs growing in the red earth of El Questro station

Boab is the common name used in Australia referring to Adansonia gregorii, the only Australian member of the genus Adansonia. Six other species are found in Madagascar and one in mainland Africa. As a group their common name is Baobab. The Boab looks alien to Australia and there are many theories as to how and when it came to be in the Kimberley but so far there is no convincing evidence to support any one theory.

Sturdy old Boab amongst widely dispersed smaller Boabs

Sturdy old Boab amongst widely dispersed smaller Boabs

The overall height of a mature tree is only about 15m while their swollen trunks can easily be 4 or 5m in diameter so the older trees can look rather squat and earth-bound but majestic none the less.

Boabs growing in ancient rocks near Tunnel Creek

Boabs growing in ancient rocks near Tunnel Creek

Boabs grow in a wide variety of habitats, including rocky outcrops, limestone hills, sandy plains and flood plains, in soils that can be rocky, sandy or loamy. They need high rainfall during the Wet or to have access to water from creeks or drainlines.

The Kimberley covers a huge area (over 400,000 sq km) so it isn’t surprising that there are areas that aren’t suitable for boabs to grow in.

Some days you can drive all day without seeing one and then in the distance you spot the striking distinctive silhouette of an old boab, standing sentinel, or a group that looks as though they have just landed from another planet, huddled together for protection.

Boab silhouette

Boab silhouette

To me they are all fascinating and I feel privileged to have seen them in their natural habitat.

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Linda Green

About Linda Green

Linda is a landscape designer and horticulturist living in Fremantle, Western Australia. In 1988 she established Hidcote Landscapes and she still finds starting a new garden design a thrilling prospect. She loves visiting inspiring gardens overseas and exploring the bush closer to home. For more information visit www.hidcote.com.au.

2 thoughts on “Boab trees of the Kimberley

  1. dani976 on said:

    Thanks for the article. Do you know how much fruit they have and how long they take to grow to fruit stage by any chance? In know they are very nutritional.

  2. Linda on said:

    The fruit may well be high in nutrition but to me they appear unpalatable when raw. A company in the Northern Territory is growing Boabs commercially as a gourmet food and they may be able to answer your queries. http://www.boabsinthekimberley.com.au/

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