I have moved to a 7 yr old house and small garden, neither of which have been well maintained. The garden contains a pretty small tree that I think is Mimosa, it is levering itself out of the ground in the wind, already nearing 45 degrees from vertical. I hope to prop it with a tree stake at 45 degrees opposite angle. It would be best to lighten the windage by pruning the head, but this is the wrong time of year. I am in Buckinghamshire, the tree is in a sheltered garden, but in a north facing border. What advice can anyone give?