This astra grew unexpectedly in a place of former compost.

nice surprise gift! so long as it doesn't get too invasive

It is not. But it looks very nice, much nicer, then on this photo, as there was a lot of sun in that corner, but in reality it is dark green with cerulean flowers. Very, very impressive.

and you got it for free, and it was a surprise gift, too! good job you didn't pull it up when you first noticed it

Yes, I knew what it was and left it there.