Pensacola News Journal

For:    Saturday, Feb. 7, 2004

By:     Daniel E. Mullins

            Extension Horticulture Agent

            Santa Rosa County

Effects of a Cold Winter Expected

            Weather is not my area of expertise, but I am often asked to make predictions and discuss the subject as it relates to gardening.  During the fall several years ago I was approached by a writer and asked to predict the kind of winter that we would have.  With tongue in cheek and cautioning that this is not my area of specialty, I made up some stuff!  My prediction was for an extra cold winter and then proceeded to back it up with folklore and some scientific sounding reasons.

            To make a long story short, the following winter turned out to be a very cold one.  Since that time I have refused to provide further weather predictions.  I figure that it is best to quit while ahead.

            We can’t all be weather experts, but gardeners should keep an eye on the current weather as well as apply information from past years.  Such information is invaluable in selecting plant species and cultivars, adjusting planting dates and in implementing cultural practices.

            The subject of “chill hours” comes up frequently, especially among fruit growers.  This serves as a good example of just how important the weather is to the gardener.  Chill hours, sometimes known as chill units, are the number of accumulated hours below 45 degrees F. that occur during a given winter. 

            Most varieties or cultivars of deciduous fruits have specific dormancy requirements.  They are bred for particular regions of the country based upon the average number of chill hours that occur there each winter. 

            The chilling requirement for peaches is so specific that there are seven different zones in Florida alone. There is even a difference between the southern and northern parts of the Gulf Coast counties.  The southern half of our counties receive approximately four hundred chill hours during the winter, while the northern half receives six hundred to six hundred and fifty chill hours on average. 

            This specific dormancy requirement is one reason that it is not advisable to plant most lilacs, delicious apples, Elberta peaches and other more northern adapted plants.  They don’t receive dormant periods that are long enough during our relatively mild winters.

            We can now more accurately monitor chill hours and obtain other important data by using the Florida Automated Weather Network (FAWN).  There is a world of weather information at this site including current and historical data.  Go to http://fawn.ifas.ufl.edu/ and learn to use the system.

            Based upon information from FAWN I can now make some predictions or at least, educated guesses about weather’s effects upon gardening.  For example, I expect a sudden burst of color this spring.

            Information from the weather station at the West Florida Research and Education Center in central Santa Rosa County, Florida reveals that we have already accumulated seven hundred and forty one chill hours through January of this year.  Since this data is collected until mid-February, it appears that we will likely have an eight hundred chill hour winter.      

            This means that the dormancy requirements of most Gulf Coast plants have already been met.  We can expect early blooms on azaleas, spireas, peaches, pears and many other spring flowering plants. In fact, the first week long period with temperatures in the seventies could result in earlier than normal and even premature flowering.

Question of the Week:  When is the best time to prune grape vines and rose bushes?

Answer:  In north Florida, the recommended time for pruning grape vines is between January 1 and March 10.  Roses are pruned during the latter part of the dormant season, usually in February.  Many rose growers choose Valentine’s Day for pruning their plants.  The timing is about right and this holiday serves as a handy reminder.

            Both grapes and roses have special pruning requirements.  If you are unsure exactly how this should be done, ask your garden center operator, landscape professional or Extension office.  There are also consulting rosarians in the area that are willing to share information about growing this popular plant.