7-10 Days to maturity. Brassica rapa Narinosa Group. Tatsoi Black Knight Mustard Microgreen Seeds. This green tatsoi microgreen is different from other tatsoi varieties in flavor. Much more like cabbage and milder in taste than other mustards. This is the mustard microgreen for those who haven’t liked other mustard greens they have tried. These tiny yet mighty microgreens open light green, and their leaves intensify to a dark green just before harvest. ~15,000 seeds/oz.