Nearly one thousand species of plants with edible leaves are known. Leaf vegetables most often come from short-lived herbaceous plants such as lettuce and spinach. Woody plants whose leaves can be eaten as leaf vegetables include Adansonia, Aralia, Moringa, Morus, and Toona species.

The leaves of many fodder crops are also edible by humans, but usually only eaten under famine conditions. Examples include alfalfa, clover, and most grasses, including wheat and barley. These plants are often much more prolific than more traditional leaf vegetables, but exploitation of their rich nutrition is difficult, primarily because of their high fiber content. This obstacle can be overcome by further processing such as drying and grinding into powder or pulping and pressing for juice. Leaf vegetables are typically low in calories, low in fat, high in protein per calorie, high in dietary fiber, high in iron and calcium, and very high in phytochemicals such as vitamin C, vitamin A, lutein and folic acid.