Rhubarb can be kept fresh, frozen, canned or dehydrated. Fresh rhubarb will remain viable for cooking for weeks after harvest, depending on the temperature and humidity. It can be kept at room temperature or in the crisper of your refrigerator. Over time it may become limp from dehydration. However, dehydration does not affect the usefulness in cooking. It is not recommended you attempt to rehydrate by resting the stalks in a container of water, a technique which works well for celery. Doing so causes rhubarb to split apart along the length of the stalk and curl. Very strange-looking.
Rhubarb is easily frozen. It will keep for a year in a freezer bag or up to three years if vacuum-packed (see photo). The texture of frozen/thawed rhubarb is less firm and considerable moisture is released in thawing. Blanching is not necessary but also not harmful. You should wash and cut the stalks as appropriate for your anticipated recipes as frozen/thawed stalks are very difficult to cut. To prepare for freezing we normally: 1) Wash the stalks thoroughly in clear water; 2) Cut them into the sizes required by our expected recipes, usually 1/2″ to 1″ long pieces, and; 3) vacuum pack them in packages from 2 cups to 6 cups. (6 cups are ideal for a single rhubarb, iced tea, and punch while 2-4 cups works for rhubarb bread, cake and smaller batches of rhubarb sauce.) Vacuum packed packages of rhubarb have lasted for years in good condition in the freezer of our regular refrigerator.
Frozen rhubarb fibers release considerable liquid when thawed and the fibers are mushy. This only affects the usefulness of frozen rhubarb when a firm piece of rhubarb is important to the texture of the dish. Since rhubarb softens and releases
moisture as a normal part of the cooking process, this means frozen rhubarb is fine for cooked recipes. Indeed, it is superior to fresh for some recipes (pancakes, brownies…anything where you want the rhubarb evenly distributed throughout the dish instead of in chunks). Six cups of 1″ rhubarb pieces will separate into about two cups of fiber and 3 cups of liquid (air between the pieces has disappeared). Simply be sure to include an appropriate amount of both liquid and fiber if substituting frozen for fresh rhubarb in a recipe. (For example, if the recipe calls for 2 cups and you have thawed 6 cups then use 1/3 of the liquid and 1/3 of the fiber in your recipe.) However, the liquid and fiber can also be used separately in many recipes. For example, the liquid is an excellent start to rhubarb iced tea and the fiber can be added alone to pancakes, muffins or cookies. Indeed, frozen rhubarb offers convenient new opportunities, beyond those offered by fresh, for adding fiber, vitamin C and calcium to your recipes. There are many opportunities for experimentation.
Rhubarb stalks can also be dried. Simply trim the ends to produce a stalk of the desired length. Clean and dry the stalk and hang it or place on a rack in a relatively dry, clean place. I’ve not tried this but the dried stalks reportedly rehydrate easily and are just as tasty and useful in cooking as the fresh or frozen stalks. This has an advantage over frozen…no need for a freezer and no risk that a power outage will necessitate immediate cooking on a massive scale! Rhubarb can also be cut to smaller pieces and dehydrated in an oven or a dehydrator.
Many rhubarb recipes are suitable for canning. These include rhubarb sauce, salsa, compote, jam, preserves, and conserve. Be sure to follow safe canning practices.