Pak choi - a green for next winter season

I'm getting together a list of greens to try out during the next winter growing season.  Pak choi is definitely on the list.  The greens on the left of the picture above are variety of pak choi called joy choi (tatsoi is on the left).  Pak choi part of the Brassica rapa var. chinensis group.  Originally we didn't think it would be a very good baby green because it forms heavy heads.  It seemed to work out in the tray above and grew faster than the tatsoi!  The stems were thick and crunchy but the taste was mild.  Pretty much exactly what I want to be eating in the middle of winter.