Depends which one, so from 66 feet to 115 feet.

I was just going to say 'big' but you are quite correct bamboo it does depend on the species and if you intend to keep pruning it.

Just to be pedantic, E. vernicosa (the Varnished Gum) is the smallest of the hardy species and grows to about five foot (try getting one though!). The foliage really does look as though it has been varnished too as even when dry, it is so shiny.

Which variety are you talking about first of all? some you can cut down every spring to keep them with their juvenile leaves.........others grow enormous very very quickly.

In there native habitat they can be 300' tall, one of the tallest trees in the world.

Yes, Eucalyptus regnans can to be specific :-) This is a borderline hardy species in the uk though.