Only has 2 branches. What can I do?
Regular watering schedule is very important in the first few growing seasons.
This will help it establish a good and deep root system.
In extreme heat, watering should be increased.
A Mimosa Tree should be planted in full sun.
Soil conditions should be light soil and well draining.
This specimen is considered a fast growing tree with a short life span.
10 to 20 years in perfect growing conditions.
It is susceptible to Mimosa Wilt and Mimosa web worm.
Here is a link with more information.