  But what the Yonces and thousands of other peach growers still
don't know is this: How does a peach know when the cold winter
weather is over and it is time to grow?   "It's an interesting
phenomenon," Clemson plant biologist Doug Bielenberg said.
"These plants count the cold hours and days. If it gets warm for
a bit, they stop, and then they pick up counting where they left
off."      "The weather controls our destiny, basically," said
Yonce, who has been growing peaches for four decades. The family
business is J.W. Yonce & Sons farm, founded by his grandfather
in 1932 in Edgefield County.   The fruit was perfect for the
area. Winter nights are cold enough for the chemical reactions
that make peaches sweet, but not cold enough to kill the fruit
as it grows. Peaches later need warm to hot weather for the
fruit to mature. That's why the Georgia joins California and
South Carolina as the nation's leading peach-producing states.
Research from Clemson and the University of Georgia has helped
up farmers conside