Wildflowers of the United States

Carolina Phlox, Summer Phlox, Thickleaf Phlox, Giant Phlox - Phlox carolina

Genus Common Name: Phlox

Native Status: Native

Dicot Perennial Herb

Phlox carolina - Carolina Phlox, Summer Phlox, Thickleaf Phlox, Giant Phlox. Phlox species can be very difficult to differentiate. Not only do several species share similar shapes in both the flower and the leaves, but the color ranges are broad and similar. You have to look at details to differentiate between many of the plants in this genus. Carolina Phlox (P. carolina) and Smooth Phlox (P. glaberrima) are particularly difficult to differentiate, with the differences being in the shape of the calyx and the sepals. Frankly, it's beyond my expertise. Fortunately I had some help with this one - this was photographed near Craggy Gardens on the Blue Ridge Parkway at an altitude between 4,000' and 5,000', and the staff there, using the location-specific ID book they have at the visitor center, identified it as Carolina Phlox. Other characteristics match, and Phlox carolina blooms later than Phlox glaberrima; P. glaberrima reportedly would be rarely blooming in late August, when these photographs were taken, while that is not an unusual bloom time for P. carolina. Carolina Phlox grows in woodland edges and openings, such as roadside on the Blue Ridge Parkway. It is reported extirpated in Maryland.

Found in:
AL, AR, FL, GA, IL, IN, KY, LA, MD, MO, MS, NC, OK, SC, TN, TX, VA

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Distribution of Phlox carolina in the United States and Canada:

Map courtesy of The Biota of North America Program.
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Site: Blue Ridge Parkway, Craggy Gardens, Buncombe County, NC Date: 2014-August-29	Photographer: Gerald C. Williamson Nikon D7000 Tamron SP 90MM f/2.8 AF Macro
As with most Phlox species, Phlox carolina usually has 5 petals. Both P. carolina and the very similar P. glaberrima are among the Phlox species with slightly exserted stamens.

Site: Blue Ridge Parkway, Craggy Gardens, Buncombe County, NC Date: 2014-August-29	Photographer: Gerald C Williamson Nikon D7000 Tamron SP 90MM f/2.8 AF Macro
Carolina phlox grows to about 30 inches tall. There may be several inflorescences, or the inflorescence may be solitary.
Click on the photo for a larger image
Site: Blue Ridge Parkway, Craggy Gardens, Buncombe County, NC Date: 2014-August-29	Photographer: Gerald C Williamson Nikon D7000
Both Phlox carolina and Phlox glaberrima (along with a few other Phlox species) have leaf margins that are smooth or slightly rough, and any lateral veins in the leaf are not readily apparent. The stems of P. carolina are usually red-streaked, I think this is a difference between P. carolina and P. glaberrima. Those streaks or spots can be seen in this photo. Weakley's keys use calyx and sepal shape to differentiate, with P. carolina having a "subcylindric" calyx with fairly broad sepals, each with a rather weak midrib, while the calyx of P. glaberrima is "subcampanulate" with narrow sepals which have well-developed midribs.
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Phlox carolina initially published on USWildflowers.com 2015-02-24; Updated 2017-03-02

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2025
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Code Update 20230302