Next to kale, collards are one of the healthiest greens you can eat. They are an excellent source of folate, vitamin C and beta-carotene while also being high in calcium (source).
Collards (Collard Greens)

Next to kale, collards are one of the healthiest greens you can eat. They are an excellent source of folate, vitamin C and beta-carotene while also being high in calcium (source).
More information about collards.