When is the best time to prune Lavatera, the tree variety?
I do the same as Verdun and take cuttings every other year.
If it is too big now, cut down by half to minimise wind rock,then cut down pretty hard in spring like you would a buddleja. When you get lots of new shoots, use a few for cuttings, as lavatera is not a long lived plant , and may only last 3 or 4 years.
Lavatera grow extremely quickly. The best time for me is to prune early to mid spring. Sometimes in October after flowering.
Here is some pruning techniques for you
I reduce by two thirds now and prune again in Spring,cuttings are very easy to take.
I only prune in Spring. Lavatera are very prone to frost damage on new growth which is why they can be short lived but they don't have to be if pruned once the weather starts warming.