In case you don’t read comments, I want to acknowledge one that made me feel silly and smarter at the same time.
The McNeelys at RockyCrop Farm told me that they ‘broadcast it after summer’s harvest of cucurbits. It blooms and dies back with frost and makes a pretty good ground cover that helps with winter erosion. Then, in spring it has re-seeded itself and grows until about 50% bloom when it is turned under early enough to decay before planting tomatoes.’
And as a bonus, they sent a link to much cheaper seed: Heavenly Seed
I love learning things.