Chard is a relatively short-season crop, so, with replantings every few weeks, we can offer it young and fresh until first frost. --Thor
Benefits and Nutrition
In general, chard provides substantial amounts vitamins A, K and C plus valuable minerals, (especially iron), dietary fiber and more protein than most vegetables on their own.
There is more nutritional information than anyone can consume while eating a proper portion of chard here on self.com.
Storage and Preserving
Fairly tough in the ground, chard is quite fragile once picked. Protect it from heat. If the stalks are bound, discard the tie. Store it in the crisper section of your refrigerator, unwashed, in a plastic bag.
Washed and dried stems and ribs can be frozen as is (below). Chard leaves should be blanched for one to two minutes and shocked, before freezing in a resealable slider storage bag, after expressing as much air as possible.
[N.B. "blanching and shocking" vegetables to be frozen is recommended for several reasons: it helps destroy any unwanted organisms that are still present after washing. It wilts the vegetables, making them easier to pack to minimize contact with air. It slows down enzymes that eventually damage the color, flavor, texture and nutritional value of frozen produce. The technique is quite simple. Bring a large pot of water to a high boil. Place the vegetables in the water. (A deep-frying basket, steamer insert, or strainer is handy here.) Begin timing once the water returns to a boil. Then remove the vegetables from the pot and put them in a bowl of ice water until they are at room temperature. Drain and dry with a light touch using a salad spinner and a towel. You may then freeze them for up to three months.]
Uses and Preparation
When ready to use, wash the chard under cold running water. Separate the tender leaves from the tougher stems and any thick ribs with kitchen shears or a sharp paring knife, and pat them dry with a towel. The leaves should be used right away. The stems and ribs will keep a few days longer in the crisper, or they may be frozen in a resealable slider storage bag for later use. (The are also welcome in your stock pot, especially as they help add an earthy umami note to vegetable stocks and soup bases.)
Besides adding them to dishes, chard leaves and stems can be prepared to serve on their own by boiling, but preferably by steaming or by sautéing in a small amount of fat. For any of these methods, cut the stems and ribs into 2 inch pieces, and cook for 5 minutes or so, before adding the coarsely chopped leaves, and cooking until tender. Season with salt and pepper to taste, and toss with any other complimentary flavor that suits your menu: toasted pine nuts or sesame seeds, chopped pistachios, dried red pepper flakes, plumped currants or raisins, dried shaved bonito flakes, lemon zest or juice, balsamic or sherry vinegar - alone or in some combinations will add another note to the dish.
If you are serving the leaves raw, remember that they are tougher than spinach and even beet greens, so shred or slice them finely when adding to a salad.