Leaf vegetable

Leaf vegetables, also called leafy greens, salad greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable. They come from many different plants, but are similar in many way. They have similar nutrition and cooking methods.
Almost one thousand species of plants with edible leaves are known. Most leaf vegetables come from short-lived herbaceous plants, such as lettuce and spinach. Woody plants of some species also provide leaves that can be eaten.
Leaf vegetables have many vitamins and nutrients.
Nutrition.
Leaf vegetables are low in calories and fat, and high in protein, dietary fiber, vitamin C, vitamin A, folate, manganese and vitamin K. Leaf vegetables are very high in vitamin K. 
Preparation.
If leaves are cooked for food, they may be called boiled greens. Leaf vegetables may be stir-fried, stewed, steamed, or eaten raw. Leaf vegetables cooked with pork is a traditional dish in soul food. They are also commonly eaten in a variety of South Asian dishes such as saag. Many green leafy vegetables, such as lettuce or spinach, can also be eaten raw, for example in sandwiches or salads.