Answer: Wait until the seeds are fully ripe and about to fall out before harvesting. Separate the seeds before planting. You can plant them now, or let them fall from the plants and plant themselves. Or, you can save them to start next spring either indoors or in the garden.
Cut the stalks back when all the flowers have faded, or if you want to save seeds, wait until after the seed has ripened. Or, you can wait until frost has killed the foliage and cut it back then.
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