Vernalization

• Peach trees must endure a certain amount of time in winter exposed to temperatures between 35 and 55 degrees Fahrenheit. This exposure to necessary cold results in vernalization. The cold exposure tempers the plant to produce hormones that lead to flower production at the end of winter. The duration of winter cold is measured in chilling hours. Most varieties of peaches need between 600 to 900 hours of chilling each winter. If inadequate chilling duration occurs, peach trees fail to bloom and therefore fruit.
  
  

Damage from Cold

• Bitterly cold air temperatures also can prevent a peach tree from flowering. In USDA zones 6 through 8, winter lows can be anywhere from 20 to 10 degrees below zero Fahrenheit. At 15 degrees below zero, flower bud tissues desiccate and die. In regions where temperatures at any time drop below 10 degrees below zero, some or all flower buds may die across the tree canopy. Peach trees will not regenerate new flower buds in winter before their normal flowering season.
  
  

Flowering Season

• A peach tree may still fail to produce fruits if the flowering season from late winter to very early spring includes subfreezing temperatures. Peaches bloom early, at a time when weather includes both warm springlike days and nighttime freezes. If blossoms open up, the tender petals and floral organs will die if temperatures dip below freezing. Frosts and freezes destroy flowers and flower buds if they are not still covered by protective sepals. Moreover, if any tiny peach fruits develop after flowering and an unusual late freeze occurs, those peaches will abort.
  
  

Pollination

• The last variable affecting whether peach trees produce fruits involves insect pollinators. Unlike sweet cherry trees, peaches do not need multiple trees nearby to ensure cross-pollination and subsequent fruit set. Honeybees remain the primary agricultural pollinator of peach trees. Cool, rainy, cloudy weather may deter bees from leaving the hive and pollinating peach blossoms. Warm, sunny days encourage bees to visit peach flowers for both pollen and nectar. Do not spray chemicals nor do activities that harm bees or prevent their access to peach trees in flower.
  
  

Recommendations

• Contact your local cooperative extension office and speak with a horticultural agent. The agent keeps abreast of current agricultural issues in your region as well as shares information, research and recommendations from your state's land grant university. Lots of peach cultivar breeding over the years led to some peach cultivars that need much less winter chilling and are known as low-chill peaches. These selections make growing peaches easier in warm-winter areas such as southern California, Florida and along the Gulf Coast. Moreover, some peach cultivars demonstrate extra-hardiness to winter cold and can potentially grow in USDA zone 5.