Without meaning to I've neglected to say anything about kale. I am not not quite sure if I like eating kale as a salad green, which may be why I haven't written anything about it.
Don't get me wrong, I love kale, but I prefer it cooked. As a baby green it seems rather frilly and tasteless compared to the other mustard greens I'm growing right now. Since I've been collecting growth data for two weeks now I can say that kale has been steadily growing, so maybe I'll change my mind by next week.
After every harvest I photograph a few representative leaves of each species. When I'm done with the study I'm going to put the pictures together along with graphs to really show the growth rate of each salad green. Right now I don't have enough data points to make a worthwhile graph, but I think the photos of kale growth look pretty nice.