It is important to know the stages of tree blossoms. At different stages of a blossom you will need to fertilize or prune. You will note that one of the growth stages of a blossom is called popcorn . . . because it does look like popcorn.
The best simplification, with the most useful compilation of information I have found was done by Fairbanks University.

❂ Topics
❂Planning
❂ Planting and fertilizing
❂ Irrigating
❂ Fruit thinning
❂ Harvest and handling
❂ Insect and disease management
❂ Pruning
Click here for the full article.
Fairbanks University has several useful studies in agriculture, husbandry and self sustainability.