Annuals, especially S. coccinea, produce lots of seeds. Are you sure they are Salvias? Some common weeds like Galinsoga look a lot like Salvia when they are small.

Coccinea and subrotunda reseed heavily for me every year. Greggii and microphylla also do although much more sparingly.

Here in England, I find that the following Salvias can seed heavily.....subrotunda, forskaohleii, interrupta, rhinosina, pratensis, and transsylvanica, and a couple of other weedy ones...can't think of the names as I don't grow them for this reason!

Wheres your heart Robin lol, I love the seed weedy ones, I am perverse like that though I do draw the line with salvia
verbenaca what a reseeding devil of a sage....Salvia caymanensis has reseeded heavily as well...........

Annette

I'm pretty sure they are salvia, not weeds.
will find out.