Experts and BHG readers answer.
Hi, In general, I don't always recommend fertilizing wisteria at all. This plant seems to thrive in poor soil and if you feed it you will discourage it from blooming because the plant will put all its energies into foliage development. If, however, you really want to feed your plant, I suggest you give it a little slow-release, general purpose, granular fertilizer in the early spring. Osmocote or any product like it would work fine.