Grasstrees do not shed their old leaves. Instead it gets packed tightly around the thick stem which is held together by the water-proof resin produced by the stem. This forms the 'skirt' often seen around the stem of grasstrees which is burned off. The skirt shields the stem from heat which is why grasstrees survive during bushfires.
Xanthorrhoeas also store starch in their thick stem which provides food and helps them to survive fires and droughts.
A good website on this: City of Joondalup
When grass plants burn it can be unsettling for those not experienced in doing it. They burn very quickly and ferociously with temperatures reaching more than 1000 degrees C during fire according to Lamont et al. (2004). But if you put your hand at the top of the plant the temperature is actually quite cool where it remains below 60 degrees C.
We have noticed that grasstrees seem to come back healthier once they burn off. They sprout new leaves and often sprout stalks soon afterwards.
We also noticed that it was not just the grasstrees that were burned that came back healthier, but also the surrounding grasstrees. The theory is that it's the smell of smoke that makes grasstrees throw stalks, flowers, and seeds as a way of letting them know that they need to procriate due to impending grass fires. Not sure if this is true, but we noticed the stalks come up on hundres of grasstrees after we started burning off the skirts on only a small amount of grasstrees.
You know that your grasstree is healthy and viable when you start seeing new green shoots coming from the center of the trunk within weeks of burning.
Our advice is:
- Do not burn grasstrees when it's really dry. It is better to do so after rain when the ground is moist.
- Do not burn grasstrees when it's windy or even a slight breeze.
- Make sure there aren't dry leaves, grass, or undergrowth that can catch fire and spread.
- Get the advice from your local fire brigade.
