We have a number of ten year old Chinese purple wisteria, some of which are experiencing a clumpy growth on the stems. These growths may be as much as 6 inches in diameter, are brown and clumpy. I see none anywhere near the root area, so do not believe this is classic crown gall. Also, other than these unsightly growths, there is no real damage to the plants; no leaf dying, flower problems, or anything. What might it be?
Wisteria Carbuncle Problem
There are several cankers and galls which can affect wisteria. Probably you should have the clumpiness examined by a professional, either at a nearby nursery or at the extension service. This link will help you locate the nearest one of those:
Meanwhile, here are a couple of articles that might offer some insights: https://www.gardeningknowhow.com/ornamental/vines/wisteria/wisteria-diseases.htm