$5/bag. Each mix contains an assortment of colorful lettuces which make a flavorful and brilliant salad. Most greens are a good source of Vitamin C, beta-carotene, folate, and dietary fiber as well as some calcium. As a general rule, the darker green the leaves, the more nutritious the salad green. For example, romaine has seven to eight times as much beta-carotene, and two to four times the calcium, and twice the amount of potassium as iceberg lettuce. By varying the greens in your salads, you can enhance the nutritional content as well as vary the tastes and textures.