My most faithful companion came along. He is used to watching me do inscrutable things with plants, bugs, tadpoles and the like. He is patient. He watches for cars while I do my stuff.
I visit each plant and take a sprig of seed capsules off each one. I figure the rest can dry in place and disperse naturally. Mowing won't hurt them now. It may even help disperse them.
I'm so happy I got some gentian seeds I just laugh when I see what was our coreopsis patch. We're going to plant an American chestnut there, anyway. With a sign and a fence around it. Good fences make good neighbors.