The American Camellia Society recommends several applications during the growing season with an organic slow-release fertilizer like cottonseed meal or a general purpose slow-release chemical fertilizer. Aged or composted manure should work fine too. Weak fertilizers like liquid seaweed, liquid fish and coffee grounds can also be applied during this time. But, try to stop fertilizing around August or September in order for the plant to easily achieve dormancy during winter.

Here is a link that might be useful: ACS - Camellia Care