Stumped by leafy greens

I was right about yesterday's tests -- math was no problem, product knowledge was much tougher. We first had some multiple choice questions, then some product identification questions where you're looking at produce on a table and have to write down what it is. Most of these were no problem, but then I got to a large, leafy green that stumped me. I tasted it -- yes, that's legal on these things -- and tasted horseradish, volatile mustard oils. I went with mustard greens. In retrospect it was almost certainly collard greens, and I feel pretty dumb about that. Of course, in the "real world" you'd order collard greens from your produce purveyor and they'd give you collard greens, no problem. Ah well.