As in spinach, chard leaves should be washed thoroughly in clean running water and rinsed in saline water for about 30 minutes in order to remove soil, dirt and any insecticide/fungicide residues. Do not wash Swiss chard before storing as the exposure to water encourages spoilage. Place chard in a plastic storage bag and wrap the bag tightly around the chard, squeezing out as much of the air from the bag as possible. Place in refrigerator where it will keep fresh for up to 5 days. If you have large batches of chard, you can blanch the leaves and then freeze them.