I have two large square pots planted with asparagus fern and yellow lantana. They spend the winter in my basement and come back every year.

I'm looking for a 1-2 foot vertical plant with blue/purple blossoms that will bloom all summer to add to these pots.

Last year I tried a generic blue salvia. It wasn't quite tall enough, needed more water than the others, and I don't see any signs of life yet.

May Night salvia might work, but I can only find that in gallon pots. Any other suggestions?