Q.Rose of Sharon tree
I have had this tree for almost 3 years. It has never bloomed with flowers, just leaves. Is there something I should fertilize with, etc.?
It's important to fertilize you Rose Of Sharon but not over fertilize.
Use an all purpose fertilizer and apply in spring and again in summer.
Over fertilizing can cause drying and browning of the plant and lack of flowers.
Here are some links to refresh you on the care requirements.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-bush.htm
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/pruning-rose-of-sharon.htm