There are many species of Grass tree (Xanthorrhoea) endemic to Australia. Two species found on the Swan Coastal Plain are Xanthorrhoea preissii (Grass Tree) and Xanthorrhoea brunonis (Graceful Grass Tree).
Xanthorrhoea brunonis could easily be mistaken for a young preissii so how can you tell them apart?

Xanthorrhoea brunonis generally has no visible trunk and grows to a height of 1.5 meters.
The flower spike can grow up to 0.3 meters flowering from October to December.
Report by Sue Ford Natural Resource Management Support Officer

One simple way is too look at a cross section of the leaves.
The leaf cross section of Xanthorrhoea preissii is diamond shaped while the cross section of Xanthorrhoea brunonis is triangle shape.

The very slow growing Xanthorrhoea preissii forms a trunk of old stacked leaf bases and grows up to 5 meters.
The flower spike can grow to over 3 meters flowering from June to December.