Choose smaller-leaved kale for tenderness and mild flavor, especially if you plan to eat the greens raw. Coarse, oversized leaves are tough. Look for moist, crisp, unwilted kale, unblemished by tiny holes, which indicate insect damage. The leaves should not be yellowed or brown. Kale stems are edible, so check to be sure that this part of the plant is also in good condition.
Kale develops a stronger flavor the longer it is stored, so most people use it within a day or two of purchase. Wrap the unwashed kale in damp paper towels, then store in a plastic bag, in the refrigerator crisper.
Kale freezes well, but may become more bitter if you don’t blanch it first. To blanch, separate stems and leaves, then place in boiling water, covering the pot, for a couple of minutes. Remove from boiling water with a strainer and put into a bowl of ice water right away to stop the cooking process. After a couple of minutes, squeeze out extra moisture, then freeze kale in small clumps on a baking sheet. After frozen, place clumps in freezer bags, removing as much air as possible before sealing and storing in the freezer. Unblanched kale will keep four to six weeks in the freezer. Blanched frozen kale will keep from eight to twelve months.
See also: Crazy for Kale? Join the Club!