We have had our wisteria in a wine barrel for 1-1/2 years. It is starting to turn yellow and loosing leaves. I don't know much about wisteria. Is this the normal season change for it? We live in California, Sonoma County. I am not sure if it is root bound, the root ball is too exposed, or if we are watering it too much or not enough. It gets morning sun, afternoon shade. Suzie Andersen
Hopefully you have used a good quality, commercial grade potting mix in your container.
It should be a mix of compost, peat and perlite to support the plant but allow good drainage.
The Wisteria should receive a fertilizer application each spring such as an all purpose formulation or even one that is suited for Tomatoes.
Look for a ratio of 5-10-5.
Check the container and soil daily, you may need to water even twice a day in temperatures above 85 degrees.
Wisteria is relatively drought tolerant, but the soil should never dry out.
Make sure that the containers drainage holes are not blocked and that excess water is draining from the container.