|One whole plant|
Hint: The common name comes from the color.
Answer below the fold.
Fire Pink: silene virginica
The 'pink' in the name refers to the zig zag cut edge - like what you get with pinking shears - not the color pink. We get several 'pinks'. Some are dianthus and some are silene.
They love rocky slopes and woods, which is just where we found ours.