The problem with Typha bulrushes

Broad-leaved Bulrush Typha orientalis at Lake McLarty

Western Australia has two species of bulrush, one regarded as native to our south-west wetlands and the other as an introduced species. However, historical reviews and examinations of herbarium specimens have bought to light that both are in fact native, causing considerable confusion for those managing bulrushes as environmental weeds. 

The two species of bulrush – Typha domingensis and T. orientalis are now known to be native to Western Australia. Both occur in the south-west with T. orientalis being far more prevalent in the Mandurah district. The bulrush was once an important food source for traditional Noongar people who refer to the species as yanget. When harvested and worked, the long, thick roots, formed an edible starchy flour.

Bulrushes are very similar in general appearance, although T. orientalis has broader or “fatter” flower spikes and leaves and less distinctive separation of male and female flowers on the spike than T. domingensis. Conservation managers and environmental groups have long been vigilant in monitoring and controlling T. orientalis in WA because of its intrusive nature to invade shallow wetland areas, often on a large scale. But does the re-classification of T. orientalis as a local native species mean it should be treated any differently now? Should we regard it as a weed?

The problem with both species of bulrush is that they can dramatically change the natural conditions of wetlands by altering the hydrology (by using more ground water), the soil and water chemistry (by adding large amounts of organic material to the soil) and the ecology (by replacing diverse plant communities with dense thickets of a single species). T. orientalis is known to be prolific in the south-west, and after becoming established in new areas has been known to prematurely dry out (or terrestrialise) shallow lakes to a point where they hold water for a much shorter time each year.  This can have a profound impact on aquatic invertebrates, the birds that feed on them and the fringing vegetation that offers protection.

The definition of a “weed” is “a plant in the wrong place” and bulrushes often fit this description.  So it seems the answer is yes, we should be vigilant about new and expanding populations of bulrush. We must also remember that bulrushes provide important habitat for various birds and other native fauna, and this needs to be balanced out with management techniques.

A question asked often is, if Typha orientalis occurs naturally in the south-west then why is it known to increasingly invade wetlands, where previously it hadn’t?  Most researchers agree that changes have been brought about since European settlement, from contributions such as land clearing, urban development and changes to fire regimes. Should we also be asking the question, does the end of traditional harvesting methods by Noongar land carers also play a role in the expansion of T. orientalis into our wetlands? Given these questions it seems there should be more thought and research into the ecology and future management of the species of bulrushes.

For more information see the following:

For botanical and historical documentation – Keighery, G. and McCabe, Steve (2015). Status of Typha orientalis in Western Australia. Western Australian Naturalist 30:30-35 For Noongar use of bulrushes – https://anthropologyfromtheshed.com/project/edible-roots-typha-bulrush/#article