Celery can be regrown from the bottom end that you typically cut off and throw away. Just put the celery bottom in a dish filled with an inch or two of water, and place it in a sunny windowsill. Once roots sprout at the bottom, you’ll see new leafy stalks growing up from the center. Transfer the plant to soil, either in the ground or in a pot, and continue to water it regularly. It will take several months to grow as big as a celery bunch you'd see at the grocery store, but you can cut stalks as they grow for use in salads and as garnishes.