Q: I have a 3-5 year old wisteria that has never bloomed. What is wrong with it and what should I do? I thought that there was nothing you could do to make wisterias not bloom! It has flourished as far as growing leaves and branches all over the place.

A: My bet is that the wisteria is still in its juvenile growth phase. Most vines and trees spend a few years growing rapidly before they have the energy to grow the specialized buds that will produce flowers. Wisteria spends the first years of its life growing toward the sun. Only when it is assured of plenty of solar energy does it make the bouquets of purple flowers we admired last month.

Another cause of your lack of blooms could be that the vine is still growing vertically. The tip of every branch of broad-leafed plants has a bud which produces hormones to control growth lower on the branch. Upright branches tend to continue growing rapidly. Horizontal branch tips grow more slowly and allow nearby buds to develop into reproductive tissue. That explains why apple growers remove the vertical sprouts in their trees each winter – those branches don’t make apples!

Train your wisteria to grow horizontally on an arbor, don’t fertilize it, remember to prune it only in summer (not winter) and you will have done all you can do to make it bloom.