All the plants are, to my eye, identical in size, shape and flower color, whatever they are. This is another plant that delights in seeding into the gravel drive, but will also seed into the border where the mother plants live. The seedlings have a very wiry texture, which distinguishes them from the normal weeds in the drive, when I'm weeding away. The flowers are born on new growth and appear in my garden at the end of May or early June. Like many of the species and cultivars, they form somewhat flat topped corymbs, appearing from a distance to be a deep, dusty pink.
Close inspection reveals that they are really a lighter pink with a dark center.
If I get busy and shear the spent blooms off immediately after bloom, I'll often get a rebloom of lesser quantity in late summer or early fall. My plants have finished blooming, for the most part, although the stem, scanned here to show the typical simple, double toothed leaf shape and alternate leaf spacing on the stem, has new flowers. This stem is young, as evidenced by the green color. Old stems are a dark, reddish brown. New leaf growth is also somewhat reddish, which adds interest in early spring.