Here is the best way to store your newly purchased greens to keep them fresh the longest.
Collard Greens - Place collards in a plastic bag and remove as much air as possible. They will keep 3 to 5 days.
Kale - Do not wash before storing, as it will spoil faster. Place in a plastic bag and remove as much air as possible. Kale tends to become bitter the longer it sits.
Romaine and other Lettuces - Wash and dry before storing in the refrigerator for 5 to 7 cays. Store separately from ethylene-producing fruits (apples, bananas, pears), as these will cause the leaves to brown more quickly.
Spinach - Do not wash before storing in refrigerator. Wrap bundles of leaves in a paper towel, then place in a tight plastic bag.
Swiss Chard - Do not wash before storing. Instead, wrap in paper towel, place in plastic bag, squeeze out air. Use within 5 days.