I fertilize all of my trees, both in ground and container, on a constant bases at every watering applying 100 PPM N using a 25-5-15/TM fertilizer. Presently almost half of my trees (5o+-) are either flushing or blooming. The only sprays I ever EVER use are horticultural oil and GA3. I really don't much like stressing any of my plants by withholding water, or wilting the leaves. If I did anything, I would rather regulate the trees by using temperature. Anyway with approximately 50 different citrus varieties I certainly don't need any extra fruit production. - Millet

I doubt, that nurseries do that.
First of all, they do not know when they sell the plants and even if, the best would be ripe fruits and blossoms together.

So how to time that ... ???

So what? I really don't care much what nurseries do. Anyway, there are some excellent citrus nurseries, and some absolutely terrible citrus nurseries in the USA. Further, I really, really, really doubt that they apply these exotic growth sprays on their trees.- Millet