Blue Glow Globe Thistle Echinops bannaticus

I grow 4 of these plants in a full sun area that gets no supplemental irrigation. The heavy clay soil has been moderately amended with compost. The plants grows full and tall every year. If not supported or trimmed during the summer, it will flop but will have new growth in the center. I've trimmed it almost down to the ground and the new growth pops up for a full 2nd display. Trimming during the summer prevents flop and promotes new blooms. Bees absolutely love it! It's also nice in flower arrangements. I've gotten only a few volunteers in 4 years. I've had difficulty transplanting the volunteers, I think because of the deep taproot. I live in a suburb south of Denver, CO zone 5b. I trim it down to the ground every fall.