Hi,
I can't give you a reason, I can only tell you the same happened for my neighbor. She planted her wisteria and it bloomed that year. In the summer it had to grow, it really took off! Now in its second year it covers half of her 70 ft chain link fence, and the blooms are half way out. Very pretty. Like you, I thought it took longer too. She doesn't do anything special to it other than train it along the fence,(she did plant it in "bought" top soil-nothing fancy" she barely waters it, just expects nature to take care of it.

How lucky you are!! I have had a Wisteria for 8 years now and it has only flowered one time.It was beautiful and the fragrance was wonderful.I have pruned it according to all the experts but so far nothing.I thought perhaps it was our severe Winter and late frost was causing the problem,but this year the Spring has been mild and hardly any frost to speak of,but all I have is leaves,no blooms in sight, I am very disappointed.

I heard that they're grafting plants a lot these days onto older/flowering rootstocks. Could be the reason?

Either way, you're very lucky. I keep delaying buying one because I don't want to wait 7 years for flowers..!

Melanie