Answer: You can feed once in the spring and once in mid-summer with a high Phosphate fertilizer (middle number), like Peters "Super Blossom Booster 10-50-10". If you use a fertilizer high in Nitrogen then you will make a healthy but tall and leggy plumeria. Plumeria only branch when they bloom, therefore if you use a fertilizer that will promote the most blooms, which in turn makes the most branches. If you find a Plumeria full of branches, then you'll know it's been a good bloomer.
Best wishes with your plumeria!
Q&A Library Searching Tips