Walking an outdoor plot once a week from early July is the only way to catch males before they open. Plants in the ground grow fast in summer, and a male that was showing nothing on Sunday can have open sacs by the following weekend, so I carry a loupe and check every node cluster on each visit. Regional timing for when outdoor regulars declare is broken down on
https://breederregularseeds.com by latitude and by strain type. Missing one round has cost me a seeded patch more than once.