I'm a botanist from Australia (where we have a few Eucalypts) and I
can vouch that part of the story about Euc's splitting rings true.
Growth of many Eucalyptus species is so fast that great tensions
build up in the outer parts of the log and unless a tree is at least
80 years old, these will split the log as the log dries out.
At this age they will certainly be too big and dense for ships masts.
Because of this we plant mainly Pinus radiata (Monterey Pine) for
our domestic timber requirements because although it grows slower and
is inferior timber, we can harvest and mill it at about 30 years of age.