Celery becomes limp when its moisture evaporates; placing limp celery in water restores lost moisture and crispness to the celery. Celery is about 90 percent water, which means the plant relies primarily on water to retain its structure.
Warm temperatures encourage evaporation, so celery should not be left at room temperature for too long. If celery goes limp, sprinkle it with cold water, seal it in a plastic bag and place it in the refrigerator. After a few hours, the celery stalks should regain at least some crispness.
Water is drawn up through celery stalks by capillary action. Capillary action is the movement of liquid within narrow spaces or porous materials due to the forces of adhesion, cohesion and surface tension. Most plants rely on capillary action and draw in moisture from dirt. The water then travels through the plant's structure via its capillaries.
If a section of celery is put into a tray of water with the root end submerged and then placed in a sunny area, new growth will sprout from its core. After the new celery grows a couple of inches, the entire piece of celery can be planted in soil with just the top leaves exposed.