The Oak Leaves are broad, thin, and flat with dark red leaves centre green. The shape of the leaf may be ovate, obovate and sometimes, elliptic. red oak leaf lettuce offers a whole slew of health benefits. It has been shown to lower cholesterol absorption, provide plenty of flavonoids and other antioxidants, and deliver pro-vitamin A, to support the immune system. Buy it online fast delivery! Lettuce provides significant amounts of vitamins A and K. They have a high water content, making them a refreshing choice during hot weather. They also provide calcium, potassium, vitamin C, and folate.