Hibiscus plant in container
Our plant's leaves are turning yellow and falling off. What might we be doing wrong? The plant is now in AZ and in the sun. Have covered it up when temps below 35 at night and move onto our protected porch. Plant branches are now spindly since most leaves are gone. Should we prune them back? This plant "winters" in AZ and summers in Eden, UT which probably makes a difference.
Your Hibiscus is likely reacting to the expose to the cold temperatures.
Tropical Hibiscus cannot withstand freezing temperatures.
Exposure to cold may send them into a dormancy, dropping their leaves and having branch dieback.
This dieback will began to occur at temperatures between 40 and 50 degrees F.
You should plan on bringing your plant inside whenever the temperatures drop below 50 degrees F.
I would wait to do any pruning to see if your plant can recover.