Although neither of the Asian greens I tried this spring held together once the heat hit, Mark and I both loved the taste of tokyo bekana and want to try it in the fall garden.  I wasn't about to spend another $3 for a tiny package that barely seeds one bed, though, so I decided to let the spring crop go to seed and collect the bounty.

Asian greens definitely fit into the easy seed-saving category since the pods dry on the plant and hang around for weeks until you remember them.  Snip off the brown seed heads when they are brittle, then thresh them any way you feel like it.  Since Mom recently gave me this great pestle, it didn't take me long to pound the seed pods into submission.

Shake your container gently and the heavier seeds will settle to the bottom, allowing you to lift most of the chaff off with your fingers.  Then blow into your box to finish the winnowing process --- the light pieces of pod will float away while the heavy seeds will stay put.  I didn't winnow all that carefully since I'm just going to be putting the seeds and debris back into the ground, but you could also pass the seeds through a screen (like a flour sifter) if you wanted them to be cleaner.

The one potential sticking point when saving seeds from brassicas is that many will cross-pollinate.  However, Asian greens share their species (Brassica rapa) only with turnips and with rape (the plants that are used to produce canola oil).  As long as you don't have any other Asian green varieties, turnips, or rape plants in bloom at the same time as your select variety, you can save the seeds with impunity.