Answer: Dianthus in general object to extreme heat combined with humidity, need at least a half day of sun and a soil that is well drained. "Doris" is one of the (de;ightful) Allwoodii hybrids and as such probably would not tolerate your summers very well. However, one that is widely available and has done well even in the Atlanta area is Dianthus gratianopolis "Bath's Pink", so you might consider that one.
For some information about the history and origin of the many forms of dianthus you might find the Dianthus Collection at the Thomas Jefferson Center for Historic Plants http://www.monticello.org/cgi-local/shop.pl/page=CHP.html of interest as well as the write up at http://www.monticello.org/cgi-local/shop.pl/page=ta_pinks.ht... entitled Pinks, Gilliflowers & Carnations: The Exalted Flowers.
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