Balga Grasstrees : The Miner's Canary?

In National Parks, Reserves, and on private property in south-western Australia, balga grasstrees (blackboys) are under termite attack, rotting, breaking off, and toppling over, due to vast accumulation of thatch. The grasstree in the photograph, with heavy thatch removed by hand to show the decay underneath, is typical of thousands. Many in Roleystone are in the same condition in long unburnt blocks. Although some do survive for decades without fire, they will most likely die when fire does, eventually occur. Had grasstrees been covered by heavy thatch when Europeans first arrived, there would have been no reason to call them "blackboys", since the black stems would have been largely hidden. Only rarely would they have produced a flower stalk, usually weak and twisted, quite unlike a spear. More likely popular names with British settlers would have been "greybeards", or "haystack trees". Early sketches and paintings consistently show them, quite clearly, as recently burnt, with black stems, little thatch, and a prominent flower stalk, like a spear.

Evidence of old fire marks from balga stems suggests that Nyoongars burnt jarrah forest, such as the ridges at Roleystone, every 3-4 years. Marri forest, on the slopes, produces more litter, and was burnt every 2-3 years. Wandoo in clayey valley bottoms, had native grass underneath, which was burnt about every two years. There are still small pockets of beautiful red Kangaroo Grass (Themeda triandra) along the Canning Valley, and on Canning Mills Road, but we will lose it altogether soon, since it cannot survive long periods without fire. Inappropriate fire exclusion can cause loss of biodiversity.

As a rule of thumb, a grasstree thatch fire lasts as long in minutes as it has been unburnt in years. A three year old thatch will flare for only a few minutes, doing little damage to the green crown. A thirty year old thatch will burn for half an hour or more, reaching an incandescent thousand degrees Celsius. Few living things can stand that. Such fierce thatch fires often kill the grasstree immediately, because the protective mantle of old leaf bases is rotted away. Where dead eucalypt leaves, or casuarina needles have formed a ‘birds nest' in the green top, the rot is exacerbated, the green top is reduced in size and vigour, and the eventual fire may completely burn the green top. If the grasstree survives the immediate fire effect, it is forced to live on starch reserves until a new top can grow. Complete replacement of the top can take a year, and the plant may die in the meantime, if its starch is exhausted.

 If grasstrees are burnt more often, when the thatch is small, and the fire brief, they flower and seed profusely, the protective mantle remains intact, the green top remains largely unburnt, nutrients in the thatch are recycled, and soil pH around the base is raised. The needles become obviously greener, longer, and thicker. Fire scars on some grasstrees along the old railway track in John Forrest National Park show annual burning by railway gangs from the 1890s to the early 1960s when the railway was operating, and these grasstrees obviously survived. Now, under long fire exclusion, they are beginning to die. So are the few grasstrees left in King's Park bushland.

There is a serious conservation problem with these old icons of the bush. Although still plentiful, the possibility of mass collapses and local extinctions cannot be ruled out. Grasstrees are like the Miner's Canary - they are warning us that something is amiss in our bushland.

We can save our blackboys in Roleystone, by clipping the thatch off regularly, and burning them every three or four years when and where safe to do so. Obviously one right next to a house cannot be safely burnt, so clipping is the only answer. If you want to burn, always check with the Bushfire Chief (Noel or Robby), and obtain a permit. Warn your neighbours, so they can close windows. Research has shown that summer burning is the best time to provoke flowering and seed set, and that is when Nyoongars did most of their burning. However, with current high fuel levels and fire regulations we cannot burn in summer. The second best time is in spring, but now, in autumn is better than no burn.

If there is big thatch, don't forget to clip most of it before you burn, otherwise the fire may be so hot it will kill the blackboy. The loose thatch can be spread and burnt separately. The ash will sweeten the soil, and the smoke will germinate native seeds. You may get some weeds germinating too, but you will get weeds if you don't burn, and you will, eventually, lose your blackboys.

balga1 Long unburnt blackboy rotting in Yalgorup National Park

 balga2.jpgCleaned off 200-year-old blackboy in John Forrest National Park, showing frequent burning from 1800 (before European settlement) up to First World War. Since then, much less frequent. Last fire at 1996.

  Fire, Water and Grasstrees in Wungong

(From The Landscape Ecology of a West Australian Water Catchment, A Curtin University Research Project)

  “You see, the Natives …they used to burn the country every three or four years…when it was burnt the grass grew and it was nice and fresh and the possums had something to live on and the kangaroos had something to live on and the wallabies and the tamars and boodie rat …It didn’t burn very fast because it was only grass and a few leaves here and there and it would burn ahead and…sometimes there’d be a little isolated patch of other stuff that wasn’t good enough to burn the time before, but as it burnt along perhaps there might be some wallabies or tamars …those animals didn’t run away from fire, they’d run up to it and you’d see them hopping along the edge of the fire until they saw a place where the fire wasn’t burning very fierce…” The late Mr. Frank Thompson interviewed in 1975 about his memories of bushfire near the south coast, before the First World War. (Thanks to Dr. Ian Abbott of CALM)


Landscape ecology is a broad, interdisciplinary approach to ecology, emphasizing the importance of history and geography. It also involves other disciplines, such as biology, hydrology, climatology, geology, and mathematics. This study poses a number of questions about the use of fire as a management tool in a West Australian water catchment. It will use the methods of landscape ecology to answer these questions, and so test three main hypotheses. These hypotheses involve grasstree conservation; pre-European traditional landscape burning by Nyoongar people; and how fire might be used in today’s social and natural context. The research has the potential, in a modest way, to contribute to an environmentally sound, economically viable, and socially responsible solution to Perth’s water problems.

The study, within the Wungong Catchment, south of Perth, involves old grasstrees and their fire history, back to pre-European times. Using this fire history a landscape model will be developed, based on patch dynamics, and an analysis of the potential for self-organising, nested fire mosaics in the flammable vegetation within the catchment and its surrounds. Self-organisation in natural systems, whereby complexity can emerge from very simple basic rules, is of increasing interest in a wide range of disciplines. It links to matters such as pattern, order, chaos, and the fractal geometry of nature.

The issue of refuges for fire-sensitive plants and animals will be given special attention, as will the health and safety of nearby human settlements, such as Bedfordale and Jarrahdale. Both these could be in great danger from a major fire in the heavy fuels of the long unburnt areas of the catchment. Remember the recent Karagullen-Pickering Brook fire? Remember also how the catchments in NSW were polluted by the ash and silt from the fierce fires there? Mundaring Weir had a narrow squeak. I hope that the landscape model developed will be a helpful stepping stone to further practical research into fire management and ecology in Wungong, and other similar water catchments.
Oh, a final quote - I've got lots of these. History is an astringent check on fashionable botanical theory. Some botanists don't like it, for that reason.

"It cannot be denied that Western Australia, as far as it is known, is generally of a rather sandy, barren nature, partly owing to the constant dryness and clearness of the atmosphere and climate and to the periodical extensive bush fires which, by destroying every two to three years the dead leaves, plants, sticks, fallen timber etc. prevent most effectually the accumulation of any decayed vegetable deposit... being the last month of summer ... the Natives have burnt with fire much of the country..." Lt. Henry Bunbury, 1837 (Thanks to Dr. Sylvia Hallam of UWA).

© David J. Ward 2005/2008
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  balga3.jpgDavid with a typical cleaned grasstree showing past fire marks. Before First World War, this site, on the Albany Highway, was burnt every 3-4 years. Recent fires have been at 10-15 year intervals, and so much more intense and destructive.  

  Poor Old Balga

I was recently walking in an area not far from Roleystone, and found these old fellas in long unburnt country. They are falling over and breaking from too much thatch, combined with decay and termite attack. They have not been burnt for decades.

Fire is the only way they can shed thatch, and recycle the nutrients, without human help with a pair of clippers. If they burn now, they will probably die, because the fire will be too fierce and prolonged.



























Up to about the First World War (later in some places), most grasstrees were burnt every 2-4 years. I have some on my block, which I burn every three years. The fire is small, and over in a few minutes, with only a short puff of smoke. The green top is only slightly scorched, and continues to photosynthesize.
The balga in the photos are 200 to 300 years old, which is older than most jarrah. We have heard a great deal from the Conservation Council of WA, and the news media, about saving the old-growth jarrah, but nothing about saving equally old balga.

I have sent the photos to the Conservation Commission, which oversees CALM. I will wait to see if any action is taken.

What do you think? Are these old icons worth conserving? Why not email the Conservation Commission yourself?

David is a Retired Senior Research Scientist with the Department of Conservation & Land Management, Western Australia, and formerly Visiting Senior Research Fellow at Curtin University School of Environmental Biology