Many people are disappointed with
  the size of their home grown fruit. 
  “Why isn’t it as big as the fruit I see in the store?” First, with
  most commercial operations, fruit is run through a packing house where it is
  cleaned and sorted by quality and size. 
  Then the larger-sized fruit are sent to market where they get the best
  price.  
Second, most commercial farms
  put into practice a sophisticated fertilization program, including tissue
  analysis, which maximizes plant nutrient usage.  Homeowners, on the other hand, do not spend that much
  time or money to optimize their fertilization program and they don’t necessarily
  have to!
There are several
  specific conditions, however, that will contribute to poor fruit size:    
- Lack of irrigation – young fruit is particularly susceptible.
- Lack of sufficient heat units, i.e., a cool growing season
- Lack of nutrients including potassium
- Desiccating winds
- Viral diseases, nematodes, root-attacking fungi, and insect infestations.
