I am not an expert in any way, so maybe others will step in here, and I don't have much experience with osmocote. If it is a water soluble fertilizer, then you may want to get something with a high middle number (Phosphorous). Plumeria use a lot of phosphorous for blooming. You also want to use a "lower" nitrogen number. I believe the standard NPK balances of osmocote are 14-14-14, which may not be a good balance for what you are trying to use it for. You may want to look into getting a fertilizer with a higher phosphorous content (though, I'm not certain what your balances are currently). Also, what kind of potting soil are you using? Definitely the more sun the better, especially given your zone. I have known some growers in the northern areas, that due to their "short summers" (compared to other places), their plumeria only bloom once every other year, rather than yearly. While your plumeria may survive with dappled or bright light for 6 hours a day, they would relish a chance to get 12 hours of light reach day--mostly being direct exposure. Is your 9 hours of sun direct sunlight for the entire day or is it dappled or shaded?
