In general, spring mix salad contains a variety of tender baby greens. The type of green can vary. Each package of store-bought spring mix will list what baby greens it contains. Baby romaine, green and red leaf lettuces, and spinach are examples of what can be in a spring mix salad. Spring mix salad greens are much softer in texture which makes it easier to chew. They are considered 'baby greens' which is why they are more tender than their more mature counterpart. Spring mix salad greens may not be as nutrient-dense as darker greens, but if it brings my kids (or anyone, for that matter) to increase their vegetable/nutrient intake, then I am all for it!