There are 28 species of the Xanthorrhoea also known as grasstree or blackboy. It is commonly believed that the Xanthorrhoea grow at a rate of about an inch (2½ cm) per century. Xanthorrhoea grow very slowly, but this is a gross underestimate: after an initial establishment phase the average rate of growth varies for each species but can be as high as about 2½ cm per year. Thus a 5 metre tall member of one of the fastest growing Xanthorrhoea would be about 200 years old.