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Warm days have folks itching to start planting warm season crops, but we know that winter is not gone for good

Read more: A Warm February is Good for Nothing

A few more rounds of cold weather are sure to come so I thought it might be good to talk about critical temperatures for fruit buds and flowers.  It seems that a warm February is becoming a normal occurrence so we need to understand a little bit about our fruit crops. 

Most of our fruiting plants and trees require a certain amount of cold weather to produce good quality fruit.  Once that requirement is met it takes a certain amount of heat units to initiate flowering.  We had around 700 chill hours as of February 15th.  Since then, we have been accumulating heat units. I am sure that you have seen the peaches and pears already in bloom. 

So what will happen if we have some days that dip down into the low 30’s or even into the 20,s?  Different plants have different tolerance to cold, and different stages of growth are better at handling cold as well.  So what are these temperatures for different crops that we like to grow?

For peaches a dormant bud can handle extremely cold temperatures.  The swollen buds that we are seeing in higher chill varieties can handle 18-21 degrees before buds are killed.  As we begin to see a little pink from the flower the flower is more sensitive and can only handle 25 degrees.  At full bloom and post bloom that critical temperature is 28 degrees.  Those are the temperatures that we can expect to see 10% bud kill.  The temperatures that would cause 90% bud kill are much lower, and the duration of the cold event also plays an important role in bud mortality.  These same numbers can also be used for plums.

For Strawberries the numbers are similar.  Buds that have not yet emerged are hardy down into the low teens.  As buds emerge they become more sensitive.  Emerged buds can handle around 25 degrees and open flowers can handle 28 if the air is dry. 

Blueberries can handle low 20’s as flowers begin to swell, and 26 degrees as the flowers are about to open. After flowers are open temperatures below 28 degrees, even for a few minutes can cause damage.

Pears have also begun to swell and bloom.  Dormant pear and apple buds can handle 15 degrees.  20 degrees can injure buds as they begin to swell.  And once you start seeing white flower parts 26 degrees can cause at least 10% mortality.  We are seeing probably the earliest bloom in the last 50 years.  This could be bad news for some of our fruiting crops if we have another cold snap or two.  If we do dodge the cold weather bullet then we will be able to enjoy a juicy Georgia peach much sooner than in a “normal” year. Contact your County Agent if you want to learn more on this topic.

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