Purple-hull peas and mustard greens in smoky potlikker

I prepare black-eyed peas every year for new years day, and so when this recipe hit the NYT web site, I was excited to try something new. I couldn't find their suggested purple-hull peas, and substituted black-eyed peas (which was suggested in the recipe). I found the flavor to be too sour - probably from the greens. I wonder if I added too many greens? The recipe specified mustard greens. I am probably too much of a botanist, because I thought about the fact that there are many different mustard plants. My market had gorgeous turnip greens, and so I went with those.

Next year back to my old standard.