A conscientious gardener, I used to tell myself, deadheads Phlox paniculata. Otherwise, since Phlox don't come true from seed, the valuable traits of a cultivar get diluted in the genetic mix. Especially mildew resistance, and color.
The species is native to much of the US, especially east of the Mississippi. They like moist, fertile soil, and full sun though they grow all over, in fields and at the edge of woods. The wild plant may resist mildew better than cultivated varieties, especially when breeders have worked mainly for color. But more cultivars now are bred also for resistance. For example white-flowered 'David' named "2002 Perennial Plant of the Year" by the Perennial Plant Association; 'Katherine' (lavender with a white eye) which performed even better than 'David' in trials from 1993-1996 at the Chicago Botanical Garden; or 'Shortwood' (a bright pink), the only Phlox paniculata found by the Ohio Nursery and Landscape Association to show "absolutely no mildew regardless of weather or crowding."
Wild summer phlox are most often rosy lavender. Over the years I've added to the gene pool in my garden with a few cultivated varieties; so now it produces a riot of white, pink, mauve, and magenta often with contrasting eyes and sometimes with spots or stripes. Occasionally I see some red but not often, because the source, 'Starfire', was so mildew-prone I tried to exterminate it. (I learned to buy only resistant varieties.) Last week I found a volunteer that's definitely purplish.
Phlox also should be given plenty of space, shallow feeding, and regular watering, because their root systems only descend about six inches, but extend out from the plant a good two feet. Even in the days when I was physically active, I couldn't keep up with all this. I would feel guilty about letting them go wild.
Now I'm learning to be more philosophical. My collection does mildew some. The phlox is spreading towards my roses, but they're all resistant ones and so far haven't caught it badly. The phlox don't have such robust flowers as they could if I fed and watered them but they still fill the August garden with bloom and butterflies.
And one volunteer an intense, almost hot pink has a nice full head of bloom even though it's in a dry, neglected location! That one, and the purple, get their seeds carefully harvested so I can spread them around.