If you collect a handful of Bok Choy seeds, you could have a fall or next-spring crop of microgreens. Broadcast-sowing them thickly and harvesting between the cotyledon and 4-real-leaf stages produces a tasty garnish or salad ingredient in 3-4 weeks, but not many mouths-full per packet of seeds.
When I had some bolt early in the summer, they developed dry. brown, cracking pods early enough that I was able to just tip the stems over a cardboard box and shake out a lot of seeds.
