"Cereoid+10+" wrote in message ...
Exactly which tree species that grows that fast would produce wood strong
enough to support a treehouse?

Grounded living tree houses don't need support. If you want to have a
house up in tree I would start with several trees already growing and
a minimum of 1/2 meter in diameter and use the spread of the trees as
a foundation. The new growth stimulated by the pollard cut could be
trained. Exactly which tree species would be strong enough remains an
unknown. It may all depend on the grafting techniques the load and the
wind and the time of year the wind blows. Hard to say for sure.
Richard Reames
Arborsmith Studios
http://www.arborsmith.com