North American Fruit Explorers mailing list at ibiblio

[Lon Rombough <lonrom@hevanet.com>]

One important factor is the temperature during bloom time and somewhat after.  We had a very warm spring this year and not only are my grapes more than three weeks early, they are much larger than usual.  This isn't just my observation, either.  Temperate Zone Pomology by M.N. Westwood says the same thing - warm weather at and just after bloom time allows the developing fruit to have more cell divisions, which can give bigger fruit.  Cool weather means fewer cell divisions in the ovary (the developing fruit) so there are fewer cells to enlarge during ripening phase, and thus a smaller fruit.
I'd bet that tree fruits in the area are smaller than usual too, unless there was a really light crop to allow the tree to throw more energy into the remaining fruits.
-Lon Rombough
Grapes, writing, consulting, my book, The Grape Grower, at http://www.bunchgrapes.com  Winner of the Garden Writers Association "Best Talent in Writing" award for 2003.