If you're looking to add a little extra boost to your wisteria's growth, Epsom salt may be the answer. This type of salt is rich in magnesium, which can help promote healthier foliage and blooms. It's also relatively inexpensive and easy to find at most nurseries or garden stores.
To use Epsom salt on your wisteria, simply dissolve 1-2 tablespoons in a gallon of water and apply it around the base of the plant. You can do this once every few weeks or so during the growing season. Just be sure not to overdo it, as too much salt can damage the roots.