Step 1Trim the tops and bottoms off the citrus, then set one down on a cutting board. Slice off the peel and pith one section at a time using a sawing motion. Holding the naked citrus over a large salad serving bowl, cut out the segments between the membranes, letting any juice drip into the bowl. Or, cut the citrus into slices and tip any juices from the board into the bowl. Repeat with the remaining citrus.
Step 2Add the greens, pomegranate seeds and celery to the bowl. Drizzle the oil all over, then gently toss with your hands to evenly coat. Repeat with the lime juice and a sprinkle of salt and pepper. Top with the walnuts and serve immediately.