IMHO, much depends upon the climate. In my 6b, they seem to grow at a moderate rate. However a friend has one planted for 18 months in 7b and it added several feet last year in it's first growing season.

Arktrees

Vigor is a genetic trait and a constant. It is related to the hand the material was originally endowed with and to things like cultivar/variety. Generally speaking, A buergerianum is a rather vigorous plant across the board. I grow them out regularly for bonsai and it's not unusual for the the species plant to put on an inch of trunk caliper in a grow season along with several feet in ht. To get a multi-stemmed tree simply grow one out as a cutting for a year and chop it off about 3-4" above the ground in the spring of its second year. Then, keep as many stems as you wish from the sprouts that will occur low on the trunk. Usually an odd number, 3 or 5, is more eye-pleasing than an even number.

Al

I had one planted in my old and it grew MULTIPLE feet per year. I was in zone 8b though, so that certainly helped.