The stalky stems in collard, mustard and turnip greens are full of nutrients and vitamins, but they also take a long time to soften. This extra time often results in over cooking the leafy green which results in mushy greens, as well as a less nutritious side dish. The easiest way to remove the stem is to fold the green in half and slide the tip of a sharp knife down the stem membrane. Then, stack the greens on top of one another and cut into bite sized cubes.