Wisteria, getting them to bloom

I have five large Chinese wisteria. All at least 15 years old. One bloomed prolifically 6 years ago but nothing since. The other four never bloomed. I keep them in full sun in Redwood City, CA.
I have not repotted in awhile so they are somewhat pot bound and use only 0-10-10 fertilizer.
Any suggestions?

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Try pruning in spring and January. I had one in Florida and one here in Washington State. They seem to be more likely to go into reproductive mode when cut back. I am training one I got at the beginning of spring. I let it grow like mad in hopes of building a bit of a trunk on it and after it grew a bit I cut it back and got a second smaller flush of racemes. I am going to put it in the ground and let it grow for a season or two next year.

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Hi Bill - how has the tree been growing for these past 6 years? If the growth isn’t vigorous, I wouldn’t be as surprised about the lack of flowers.

As for the fertilizer, you might try a balanced fertilizer in lieu of the 0-10-10. It also sounds like the tree is due for a repot.

Dan Pearson in his recent publication “Natural Selection - A Year in the Garden “ recommends ‘allowing Wisteria planted in the ground to grow freely all summer. Retrain it horizontally to create a main framework prior to cutting back to 8 buds in August. Cut all shoots back to 2 buds the following February’.
I believe it was also his observation that a potted Wisteria grows most happily when the pot sits in a dish of water all summer.
If your Wisteria is root bound, adequate water may be the problem although I suspect that the horizontal framework is also important.

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