I believe they come from root runners. I started with one plant and that has now spread maybe 40" wide. The bloom is always the same. I accidentally pulled up a piece while weeding a couple of years ago and it had a long root attached from the mother plant. I planted it in the grass bed. Which has now spread (I think this is the third year for it here) out 2 feet or so. Last year, it bloomed exactly the same.

It is a tender perennial, but comes back well for me each year. The botanical name is salvia guaranitica. They refer to its roots as tubers.

Here is a picture of my younger plant and its spread:

Helen, thank you. Your photo looks exactly like what I have here. So I should have a nifty display of B&B this year and hopefully years to come -- good news.
Sunny

Thank Glenda and I thank her too because I mulched so heavily that mine is just now coming up and I forgot what it looks like. By the way Sunny, how do you like your Forest Pansy redbud. I see very small plants at the botany shop for $20 worth it if it is superior to the native red bud.

Helen, I don't think I have a Forest Pansy redbud. I just have several full-grown redbuds that have been here forever. That must have been someone else -- my curiousity is piqued, though, so now I want to see one.
Sunny

It may have been me that mentioned Forest Pansy. I posted a photo for you.
My Black and Blues look like Glenda's photo - sprouts coming up away from the center.
A couple of my bigger plants that made it through last winter haven't come up yet this year. I thought they would be most likely to survive. I'm glad I planted more. My species guaranitica finally came up.