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Climate and Turfgrass Research
Fort Lauderdale Research and Education Center

The South Florida heat island

Philip Busey

Minimum temperatures and turfgrass research  
January total hours below minimum temperatures at four Florida locations.  Total of Jan. 24-31, 2001 and Jan. 1-12, 2002, the only dates for which complete data were available at the time this was prepared.    

To be relevant, field research must consider at the least the obvious factors, such as temperature, that can affect experiments and plant recommendations.

The graph represents IFAS Research and Education Center data from 2001 and 2002, derived from FAWN, http://fawn.ifas.ufl.edu and based on all dates for which there was complete data in January.

Among four Research and Education Centers, there is a large difference in the number of hours below 52 degrees Fahrenheit (11 C), the temperature at which warm-season turfgrasses begin to show winter chill injury.  In the study period, the FAWN weather system recorded essentially zero hours below 40 F for both Homestead and Fort Lauderdale.  Fort Lauderdale was warmer than Homestead, because it is part of a heat island that is also shown in the USDA Plant Hardiness Zone Map.

In terms of plant performance, winter cold can be very important.  The vast majority of golf courses in South Florida (urban Miami-Dade, Broward, and Palm Beach counties) do not overseed with cool-season turfgrasses.  In northern Florida, most golf courses do overseed.

Because Florida is very attenuated from South to North, there are several climate zones, based on average annual minimum temperature.  Based on the USDA Plant Hardiness Zone Map, most of South Florida is in climate zones 10b and 10a, with average annual minimums below 40 F.  Gainesville, located in Alachua County in northern Florida, is in climate zone 8b, with average annual minimums below 20 F.  		 
   
 
Table 1.  Average minimum
temperature,
December to February
Location (F)
Fort Lauderdale 50
Homestead 49
Belle Glade 42
Fort Pierce 41

By comparison, to cross another full two climate zones along the Atlantic, one would have go to the interior of New Jersey and coastal Massachusetts, zone 6b, with average minimums below 0 F.  Consequently, and based on average annual minimum temperature, field research on plants performed in Gainesville would be about as relevant to New Jersey and coastal Massachusetts as it would be to South Florida.

Clearly, we cannot place field research in every possible environment.  However, for urban landscape plants such as turfgrass, it would be most efficient to place such research in the climates of the major urban centers, which are South Florida, Orlando, Tampa Bay, and Jacksonville.

Reference:

USDA Plant Hardiness Zone Map, South-East US, http://www.usna.usda.gov/Hardzone/hzm-se1.html

Growit.com FLORIDA USDA Hardiness Zone Map http://www.growit.com/bin/USDAZoneMaps.exe?MyState=FL

 
   
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