Now is the time . . . all those dried out remnants of summer love are stuck like beheaded cannibals atop the varying heights of flower stalks. You could just look at them, but what fun is that? Snap 'em off, do a little reading, and figure out how to save, start, and grow them on for next year!
It never ceases to amaze me how ONE, just one, flower will make enough seeds to litter your garden like a ticker tape parade after the Yankees win the World Series. Considering their winning streak, ahem, I'm just glad that life has rhythms that do not depend on major league baseball.
Those gorgeous pods are from Baptisia australis, a fantastic US native. Even if you don't care to grow on the seeds that are ripening now, cut them and use them in fall floral arrangements, or for other decorations for the season.
If you really are serious about collecting seeds, its very simple. You'll just need some envelopes, a pen, and something to cut the seed head off (sometimes you try to break it off and, well, you know Murphy's Law).
Label your envelope with the name of the plant (duh), the date, and where it was collected. Then go ahead and harvest those seeds! Do not be selfish; leave some seeds for others, as well as for that precious plant that worked so hard attracting pollinators in order to procreate itself. Next, seal the envelope and put in the fridge until you know what you are doing with them.
Don't forget to marvel at the unique shapes, textures, and scents of those seeds. Have fun!