Q.Jacaranda Dropping Leaves, Limbs
I have a young potted jacaranda and am in zone 9b in the Sacramento area. I got it in April 2020 and it added some 7-8 inches of new growth for 6 months. It stopped growing around late October but stayed evergreen until late January when the leaves began to slowly turn light green to yellow and fall off. That was not a concern until even limbs began to easily break off. Even with our mild winters I always brought in at night only leaving outside during the day. I can’t find any pictures online on what a normal Jacaranda looks like in a zone 9b winter. Do small Jacaranda saplings also drop small limbs in late winter? Is this normal?

Certified GKH Gardening Expert
Likely, it is lacking in nutrients. Trees in container use nutrients very quickly. They must be replenished occasionally to make up for this.
The tree is hardy in your area, though. Planting in the ground will give it a much better chance for survival. If you do choose to keep it in a container, then you may want to size up to avoid the tree becoming rootbound.
Here is an article that will help you with the care of the tree:
https://www.gardeningknowhow.com/ornamental/trees/jacaranda/jacaranda-tree-information.htm