Leaf vegetables, also called leafy greens, pot herbs, vegetable greens, or simply greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. Leaf vegetables eaten raw in a salad can be called salad greens.
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 of various species also provide edible leaves.
The leaves of many fodder crops are also edible for humans, but are usually only eaten under famine conditions. Examples include alfalfa, clover, and most grasses, including wheat and barley. Food processing, such as drying and grinding into powder or pulping and pressing for juice, may involve these crop leaves in a diet.
Leaf vegetables contain many typical plant nutrients, but their vitamin K levels are particularly notable since they are photosynthetic tissues. Phylloquinone, the most common form of the vitamin, is directly involved in photosynthesis.
Spinach, as an example of a leaf vegetable, is low in calories and fat per calorie, and high in dietary fiber, vitamin C, pro-vitamin A carotenoids, folate, manganese and vitamin K.[1]
The vitamin K content of leaf vegetables is particularly high since these are photosynthetic tissues, and phylloquinone is involved in photosynthesis.[2] Accordingly, users of vitamin K antagonist medications, such as warfarin, must take special care to limit the consumption of leaf vegetables.[3]
If leaves are cooked for food, they may be referred to in the United States as boiled greens. Leaf vegetables may be stir-fried, stewed, steamed, or consumed raw. Leaf vegetables stewed with pork is a traditional dish in soul food and Southern U.S. cuisine. They are also commonly eaten in South Asian dishes such as saag. Leafy greens can be used to wrap other ingredients into an edible package like a tortilla. Many green leafy vegetables, such as lettuce or spinach, can also be eaten raw, for example, in sandwiches or salads. A green smoothie enables large quantities of raw leafy greens to be consumed by blending the leaves with fruit and water.
In certain countries of Africa, various species of nutritious amaranth are widely eaten boiled.[4]
Celosia argentea var. argentea or "Lagos spinach" is one of the main boiled greens in West African cuisine.[5]
In Greek cuisine, khorta (χόρτα, literally 'greens') are a typical side dish, eaten hot or cold and usually seasoned with olive oil and lemon.[6]
At least 80 different kinds of greens are used, depending on the area and season, including black mustard, dandelion, wild sorrel, chicory, fennel, chard, kale, mallow, black nightshade, lamb's quarters, wild leeks, hoary mustard, charlock, smooth sow thistle and even the fresh leaves of the caper plant.
Preboggion, a mixture of different wild boiled leaf vegetables, is used in Ligurian cuisine to stuff ravioli and pansoti.[7] One of the main ingredients of preboggion are borage (Borago officinalis) leaves.Preboggion is also sometimes added to minestrone soup and frittata.[8]
Botwinka (or boćwinka) is a soup that features beet stems and leaves as one of its main ingredients. The word "botwinka" is the diminutive form of "botwina" which refers to leafy vegetables like chard and beet leaves.
In the cuisine of the Southern United States and traditional African-American cuisine, turnip, collard, kale, garden cress, dandelion, mustard, and pokeweed greens are commonly cooked and often served with pieces of ham or bacon. The boiling water, called potlikker, is used as broth. Water in which pokeweed has been prepared contains toxins that have been removed by boiling and should be discarded.[9]
Sauteed escarole is a primary ingredient in the Italian-American dish Utica greens.
See main article: List of leaf vegetables.
Postharvest diseases cause up to 50% losses of leaf vegetables. These are fungal, bacterial, and much less commonly viral. The most important remedy is temperature-controlled storage, although it is also important to prevent mechanical damage as this provides entryways for pathogens. Uncontaminated water for washing vegetables is of lesser but still significant importance.[10]
Common bacterial pathogens include: Xanthomonas campestris pv. vitians, Pseudomonas viridiflava, P. cichorii, and P. marginalis, P. syringae pv. aptata, X. campestris pv. campestris, X. campestris pv. raphani, P. syringae pv. maculicola, P. syringae pv. alisalensis, Pectobacterium spp. including Pectobacterium carotovorum subsp. odoriferum and Pectobacterium aroidearum, Dickeya spp., Pseudomonas marginalis, and Pseudomonas viridiflava.
Common fungal pathogens include: Alternaria brassicicola, A. alternata, A. arborescens, A. tenuissima, A. japonica, Colletotrichum higginsianum, Colletotrichum dematium f. spinaciae, Microdochium panattonianum, Stemphylium botryosum, Cladosporium variabile, Cercospora beticola, C. lactucae-sativae, C. brassicicola, C. acetosella, Botrytis cinerea, Golovinomyces cichoracearum, Podosphaera fusca, Erysiphe cruciferarum, E. polygoni, E. heraclei, Sclerotinia sclerotiorum, and S. minor.
Common oomycete pathogens include: Albugo occidentalis, A. ipomoeae-aquaticae, A. candida, Hyaloperonospora parasitica, Bremia lactucae, Peronospora effusa, and Peronospora farinosa f.sp. betae.
Fungicides such as prochloraz can be used to manage some of these.