David WE Roberts wrote:
I am tempted to leave it to see what it will do next year.
If it survives the winter, the options are to just let it get on, and
hopefully seed the bed for future years, or prune it back medium to hard in
the spring to see if it will produce a reasonable amount of flower on new
growth.

Anyone tried this?

I've had wallflowers (I think!) that have grown ok one year, then gone
totally mad the next, and totally taken over my planter by the third. Not
done deliberately, just didn't like to take the plant out whilst it was
still 'happy'.

My main problem is that they seem to get quite straggley (like unpruned
lavender does)