Hello, Sarah. Potting medium should be changed every now and then (usually every three years but some people do it more often). If you detect that the roots are starting to grow in circles then you need to repot in a bigger container and with new medium.

The problem that you describe however, could just be old camellia leaves falling (think dogs and shedding time!!! LOL). This happens about every two years mostly during the months of May and June. Pine trees shed leaves like this too but they do it in the Fall.

If you live near the coast (USDA Zone 8), you might be able to grow the camellia in the ground (ask a local nursery). I saw some around Vancouver (VanDusen Botanical Gardens) a while back but they were not blooming at the time. Newer varieties can grow in USDA Zone 7.

Luis

Here is a link that might be useful: American Camellia Society's Container Info