I do not know what the wholesalers use but it may be much more than is necessary since they sell more if the shrub is loaded with flower buds.

Below is a link to the American Camellia Society's suggestions on how to fertilize. On newly planted camellias, I use cottonseed meal or composted manure. About 1/2 cup to 1 cup for a newly planted shrub. I have also used a slow-release general purpose chemical fertilizer (Osmocote 10-10-10).

Luis

Here is a link that might be useful: Camellia Fertilization

Thank you Luis. You are not far from me, I am in Arlington. Old Camellias are all around my old neighborhood. I am happy to learn that I can fertilize again, this is more than I have done before.
smiles cynthia

Cynthia, You can also buy a camellia/azalea fertilizer, formulated for acid loving plants. I used this on my plants in the begining to help get them off to a good start. My soil is pretty good and I keep lots of mulch whether it is pine straw, leaves, pine bark or a mix of this with grass clippings, So I honestly have not fertilized in two years. The growth rate is great on all my camellias. If you have unimproved sandy soil I would add as much mulch around all the shrubs to beyond the leaf line and I would use fertilizer as sandy soil leaches nutrients pretty fast but if you have reasonably good soil fertilizer just to keep them healthy. I think usually the recommended rate is three times per year, but like I said Mine seems to be totally happy they are all dark green and luxurious and have had plenty of buds every year. Hope that helped you some.
James in Florida