It is important with Swiss chard to continuously harvest the foliage as it reaches 8 to 12 inches. Older, tough leaves left on the plant will prevent the plant from producing fresh foliage. Leaves should be cut with a sharp knife, 1 inch above the ground. Continue to harvest in this way until fall. Take care not to damage the new inner stems and growing points.
Harvested chard can be stored unwashed in the refrigerator for a 7 to 10 days in plastic bags.
Freezing Swiss Chard
Chard can be frozen and can be stored for three to four months. Separate leaves from the stems. Rough chop the leaves and blanch for no more than two minutes; immediately into ice water for 3 or 4 minutes. Spin dry the chard and place in freezer quality plastic bags. Some folks cut the stems into slices and freeze them for adding to stews and soups.