I have a Michalia Alba in a sunken bed in a court yard in San Jose CA. This is Sunset zone 14, USDA zone 9B. The court yard faces west but the tree is blocked from western sun by the house. It gets direct sun from about 8:00 am to about 12:30 PM. The sunken bed is 18" deep and is full of potting mix containg mostly organics with about 15% sand. The tree is about 4 years old and is about 12 feet high. It blooms well and the leaves do not get sun burn. During cold snaps the leaves do get some burn. It is on a drip system with hard wate, about 300ppm Ca, but the leaves do not get much tip damage.
How tall will my tree get?
Can I prune it into an "umbrella shape" at the 15" level to keep it below the the roof line?
Thank you for the inputs,