Answer: There are several reasons why wisteria may not bloom. One is that if the plant was grown from seed rather than grafted or rooted cutting, it may simply be too immature to bloom. These vines can often take 8 years and 20 years is not unheard of to reach blooming maturity. In this situation there is not much you can do to force it along. Another reason may be overfertilizing with nitrogen, especially if it is in an area where the roots regularly receive high nitrogen lawn fertilizer plus garden fertilizer. Overfertilizing can lead to excessive growth but lack of bloom. Yet another reason may be frost damage to the flower buds. Another cause can sometimes be improper pruning. Here is a link to information about how to prune or train these vines, it also includes a general care overview.
I hope this helps!
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