Young trees

Tate's Grass Tree (Yacca), Kangaroo Island, Australia.

Xanthorrhoea is a genus of flowering plants native to Australia. There are
28 species and five subspecies of Xanthorrhoea. They are commonly known
as Grass Trees or Yacca (in South Australia). All are perennials and many,
but not all species develop an above ground stem. This is rough-surfaced,
built from accumulated leaf-bases around the secondarily thickened trunk.
The trunk is sometimes unbranched, some species will branch if the growing
point is damaged and others naturally grow numerous branches.

It is commonly believed that the Xanthorrhoea grow at a rate of about 25
mm per century. They do 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 25 mm per year. Thus a five
metre tall member of one of the fastest growing Xanthorrhoea would be
about 200 years old. A slow one may be some 600 years old.

woodgroupsa.org.au/wSAknowledge/grasses.pdf

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