Celery is a root vegetable with a high water content. The challenge when keeping celery fresh is preventing the water from evaporating. When the cells inside celery lose their water content they collapse, leading to the celery stalks becoming limp and rubbery. When stored at 32 degrees Fahrenheit, with humidity levels of between 98 and 100 percent, celery can stay fresh for two to three months. There are several ways to keep celery fresh without refrigeration, depending on your situation. You can leave the celery in the garden, store it in a root cellar, pack it in a cooler or keep it fresh for several days at room temperature if you store it properly.
Keep celery in the garden as long as possible. It can stay in the ground until there is a hard frost. Some people grow their celery in a trench, covering the stalks with dirt to keep the stalks from turning green. Celery grown in this matter is protected from the cold by the dirt, and can stay in the garden for up to one month after the first frost. To store celery longer in the garden, dig the plants up, leaving the roots attached. Dig a trench about a foot wide and two feet deep and stand the heads in the trench. Keep them close together. Water the roots, and cover the trench with a board. Top the board with soil and a mulch of straw. The mulch and the depth of the trench should keep the celery from freezing in most areas.
Move celery to a root cellar for longer term storage. Depending on the temperature and humidity in your root cellar, they celery will last from two weeks to two months. Shake off any loose dirt from the celery heads and trim the leaves down to 1 inch. Handle the celery carefully, being careful not to bruise it. Store the celery covered by hay or similar mulch to keep it moist.
Use a cooler to replace a refrigerator if you are going camping or are temporarily without power. Wash and trim the celery, and wrap the head in aluminum foil. Place the foil-wrapped celery in a plastic bag. Do not place the celery in direct contact with freezer packs or ice blocks as that may cause parts of the celery to freeze. When celery freezes, the water inside it expands and the cells burst, causing the celery to become soft.
Wrap the celery in butcher's paper and place it in the center of your backpack when hiking. Make sure there is nothing next to the celery which could bump into it and bruise it. The celery will stay good for three to five days, depending on the season and the temperature.
Wash and trim the celery, then place it celery in a bowl of cool water to keep it fresh while at home if you don't have access to any of the other methods. Change the water daily to prevent spoilage. Keeping the celery hydrated will maintain the osmotic pressure in the cells that keeps the celery crisp.