Kind of late to post on this one but.... I have found containers are not the way to go. Unless you design the soil for the container so it drains fast. Then you have more or less taken away the advantage of the container. The humidity and large rain falls in short periods can really knock down a plant or tree. I purchased a bunch of containers and now have gone to ground plantings. If you have just a few and do not mind the extra work then it will be ok. Make sure the soil drains fast and the bottom does not stay wet.

I would test the soil before I put in a big tree. I had to hand dig out a bunch out of 30+ gallon containers.

Jim

You dont need boxes, Have you been successful.
Do know which tree to grow in the coast ?
B. Shah