Why does the farmers market promote its facility as a place to buy from farmers? The only produce I see there was grown many miles away and shipped. What we really need is a amrket, or an area of this market, that sells real locally grown produce. And some organic products would be nice, too. Yes, the prices are cheaper than the grocery, but vegetables sitting in the heat and sunshine loose nutrients.
My visits to the Farmers Market indicate that the new sheds at the market effectively shade most items (and customers) throughout the day, especially the peak times of sun. And with the turnover volume, I doubt much is exposed very long to begin with. Contrast this with the grocery stores who are probably gassing or treating their produce to keep it looking picture perfect for display. Add the stores "mood" lighting to bring out the best colors and good luck bringing home exactly what you thought it was in the store.
One should also consider the many traditional varieties of produce with superior flavor that can be found in the Farmers Market that grocery stores won't touch because of their less than perfect appearance or shorter shelf life. Smart buyers know appearances can be deceiving with some produce in terms of obtaining best flavor. We didn't always have pesticides, genetic engineering, and other technology to alter produce to make it so picture perfect and old timers will tell you that much of the best flavored stuff doesn't always look the prettiest.
Many vendors are seasonal farmers and many of the regular vendors are supplied by farmers who don't wish to hang around and sell their production. A lot of the farmers sell out early in the day and you have to be there earlier to catch them. Remember, too, there is a significant wholesale operation in the early morning and farmers like to sell out quickly and get back to the farm.
With fewer and fewer farmers in the region (see below data from last week's Florida Times Union article showing that in Duval County acreage has shrunk some 73% over the last 52 years) it is not as easy to find very close-by suppliers. I would consider any farmer from Florida, Georgia, or the Carolinas "local" by today's standards. Yes, there are some vendors that mix in or carry other produce because it is nearly impossible to have enough variety and supply year round depending only on "local" production. And some of the ethnic or specialty produce may not be grown locally. You should ask questions if this is important to you and buy accordingly. But it is not right to whitewash equally all the vendors and/or the produce sold as there is way too much variety and seasonality.
By the way, if someone wants something special in the market, some existing vendors may be able to bring it in. Or, maybe you could find a new vendor to set up shop there if you see a niche not being covered. It is, after all, the ultimate in entrepreneurial settings.

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Per the Florida T-U:
SHRINKING FARMLANDThe number of farms and farmland in Duval County has been dwindling over the years, according to the U.S. Department of Agriculture's census:
1950975
farms
112,543
acres
2002382
farms
31,241
acres
Note: The 2002 figures are the most recent available; they will be updated in February.