Depends what you mean by 'fast'. They can put a foot or so on a year and are not for a small garden.

Its as well to remember that usually things that grow fast grow huge. Silver birch can end up at 30m and pruning them ruins the shape and the whole point of having them.

In full sun, good soil and well watered, they can grow fast, esp from a small 5cm whip to a 6ft in 1-2 years.

thanks so much to all kind regards

In 14 years (planted for the millenium) they are huge......and the one planted 20 years ago at its full height.
When we moved here there was one not far from the house that was having the patio slabs up,and had to go the above trees are seedlings of that tree