I have a wisteria vine that is healthy, and over 20 feet tall. This plant is three years old and has never bloomed. What can I do to get it to bloom?

Congratulations! You are well on your way to a blooming wisteria. A little basic biology may help you understand why it has not yet bloomed and what you can watch for to insure it does bloom. Wisteria seems to be a vine that thinks it is a tree; they can be so heavy that they need heavy duty support. That being said, your 3-year-old is just a baby and is not ready to bloom and set fruit (what plants do when they mature). The wisteria is a member of the pea family and the blooms are the precursor to pods (fruit). Be patient and do not start fertilizing; being members of the pea family, they are nitrogen fixers and form nitrogen-containing nodules on their roots. Overfertilization can stimulate foliar growth, but will not encourage blooming. Feeding it once a year with super phosphate to encourage root growth is about all it needs.