I am sorry for this delayed reply to your gardening question. We are transitioning to a new Q&A system and your question was unfortunately lost in the transition. I have discovered it now and hope this reply is not too late to be of help.
The trees you mentioned are pretty messy at times of the year to plant over a pool. The golden rain and honey locust will not like soggy-wet conditions either. In general I think fast growing trees like Empress are not a good investment. It is better to plant quality long-lived species and the water and fertilize them to get maximum growth rate. Also keep weeds away from the base by mulching a large area around them.
Celeste fig is fairly fast growing and will get 20 feet tall in time. However your winters will kill it to the ground is some years so it will then take off growing again in spring. The winters should tend to keep it smaller. Redbuds prefer shade but can take sun if you keep the soil mulched and moist but not soggy wet.
Thanks for the question. Please stop in again soon!
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