I have calculated chill hours for Orlando based on the FAWN weather data. I thought you may find this useful since you have posted similar information on your very informative and interesting blog.Of all the complexities of Florida gardening, this one is particularly vexing: We cannot really grow much in the way of tropical fruit like mangoes and bananas. Sure, in a limited way, we have some success--some years, I get more bananas than I can eat. But, as has been the case for the past two winters, other years my bananas get burned down to the ground (delaying fruiting by a year or more), and my mango tree dies despite my best efforts.
Chill Hours* for Orlando Winter Calculated 1997 1998 160 1998 1999 184 1999 2000 249 2000 2001 387 2001 2002 196 2002 2003 383 2003 2004 247 2004 2005 203 2005 2006 255 2006 2007 143 2007 2008 136 2008 2009 325 2009 2010 468 Average: 257 Minimum: 136 Maximum: 468 * number of hours the temperature is below 45 degrees F and above 32 degrees F
So instead of tropical fruits, we try deciduous low-chills, like tropical peaches, persimmons, pomegranates, low-chill apples and pears, etc. Years with cold winters yield heavily, while years with warm winters result in low flowering and fruiting, sometimes no crop at all. This past winter was so cold that my pomegranate is still flowering in mid-July! My peach tree bore heavily, my apple tree set fruit for the first time, and so on.
Having done a lot of shopping for such trees, the sweet spot seems to be 250 hours or more--it really expands the variety of trees (if you believe the chill-hour requirements that growers list... I don't, mostly).
DeLand is a few degrees cooler than Orlando, so it's safe to add ten or twenty hours to the numbers above. That still means that every other year, or maybe every third year, is well under the minimum "ideal" of 250 hours.
So, just barely cold enough for temperate, not quite warm enough for tropical.
I guess there's always citrus!