Use both the stalks and leaves of bok choy for stir fry. Add the stalk slices first. Add the leaves just before serving as you would bean sprouts.
Don't throw away lettuce, greens, celery, etc that has been in your refrigerator a little too long and gone limp. Revive most leafy vegetables by cutting a small amount from the stem-end, soaking in warm (100 degree) water for 5 minutes, drain and refrige