Store romaine at an ideal temperature of 33-35 degrees F. Do not allow the temperature to go below 32 F., as this will damage the leaves.  Keep box tops closed as the waxed cardboard helps retain the moisture.  Store individual unwashed, whole heads in plastic bags to retain natural moisture. Romaine will keep for a 7 to 10 days this way. Keep away from apples, as ethylene gas they give off will turn the romaine brown.