Pea (Pisum), a genus of plants of the natural order Leguminosæ, sub-order Papilionaceæ. Two species, supposed to be natives of the south of Europe and of the East, are very extensively cultivated for their seeds (peas), which are the best of all kinds of pulse—the Common Pea or Garden Pea (P. sativum) in gardens, and the Field Pea (P. arvense) in fields; both of them climbing annuals, with pinnate leaves, ovate leaflets, and branching tendrils in place of a terminal leaflet; the garden pea distinguished by having two or several flowers on each flower-stalk, the flowers either red or white, more generally white, and the seeds subglobose; the field pea having one flower on each flower-stalk, the flowers always red, and the seeds angular from crowding and compression in the pod. But it is not improbable that they are truly one species, of which the garden pea has, through cultivation, departed farthest from the original type. Peas have been cultivated in the East from time immemorial, although the ancient Greeks and Romans do not seem to have been acquainted with this kind of pulse. Its cultivation was apparently introduced into Europe very early in the middle ages; and it now extends from warm climates, as India, even to very cold latitudes, the plant being of rapid growth and short life. The pea does not appear to have been cultivated in England even in the time of Elizabeth. According to Fuller, they were then brought from Holland, and were accounted 'fit dainties for ladies, they came so far and cost so dear.' The seeds of the garden pea are used for culinary purposes both in a green and in a ripe state, as are also the green succulent pods of some varieties, known as Sugar Peas or Wyker Peas, in which the membrane lining the inside of the pod—parchment-like in most kinds—is much attenuated. Field peas are used both for feeding cattle and for human food. For the latter purpose peas are often prepared by being deprived of the membrane which covers them, in a particular kind of mill; they are then sold as Split Peas, and are much in use for making Pea Soup. They are also ground into meal, which is used in various ways, chiefly for making a kind of pottage and unleavened bread. In the countries bordering on the Mediterranean peas are roasted in order to eating.
There are innumerable varieties of the garden pea, but very few of the field pea, those of the former being so much the products of horticultural art that they cannot be preserved without the utmost attention. Some of the kinds of garden peas have long stems, and require for their support stakes 6 or 8 feet in height; others are of humbler growth; and certain dwarf kinds, preferred as most convenient in many gardens, succeed very well without stakes. The largest kinds are sown in rows about 4 or 6 feet asunder. In Britain garden peas are sown at different times from January to the end of June in order to secure a supply of green peas during a considerable part of summer and autumn; and in the southern parts of the island they are also sown in the end of autumn, a very little protection being sufficient for them during the winter. In the United States early peas are sown either in November or in February or March. Certain small kinds of very rapid growth, known as Early Peas, formerly preferred for the first sowings, although less productive than many others, are now being supplanted in the estimation of gardeners by larger and superior flavoured sorts, which combine the desirable quality of extreme earliness with the size and tenderness of the wrinkled marrow kinds.
Chalky and other calcareous soils are particularly suitable for peas, if to be used green, and in other soils a good field-crop is seldom obtained unless the land has been well limed, or manured with gypsum. The free use of lime is found to be unfavourable to the quality of field peas which are intended for human food, as peas from soil so treated do not readily melt or 'fall' in boiling, and are therefore more indigestible.
Market-gardeners in good districts in England find the pea a most profitable crop. Surrey, Bedfordshire, and Essex are the principal counties whence the supply for the enormous demand for green peas for Covent Garden Market is chiefly drawn. Supplies also are received from France in May, but are inferior in quality to the English. Peas are cultivated to a considerable extent as a field-crop in Britain, but are best adapted to those districts in which the climate is least moist, the seeds being very apt to grow in the pods when moist weather prevails in autumn, by which the crop is injured or destroyed. The most productive kinds, being also in general the most bulky in straw, are very apt to lodge before the pods are filled in wet seasons, and particularly on rich land. The crop is, therefore, rather a precarious one.
The haulm or straw of peas is used for feeding cattle; and for its sake field peas are often reaped before they are quite ripe, great care being taken in stacking the straw to provide for ventilation, so that it may not heat. Pea haulm, when cut and dried green, is more nitrogenous and more nutritious than hay.
Land to be sown with field peas should be very clean, and in particular free of couch-grass; otherwise the best management cannot prevent its becoming more foul whilst bearing the pea crop. The seed ought always to be sown in rows not less than 20 inches apart. Various means are employed for sowing peas; they are not unfrequently ploughed under the furrow; but the seed ought not to be buried more than 4 inches under the surface. In the harvesting of peas the sheaves are generally left loose till the haulm is somewhat dry. In drying it shrinks very much. Winter Field Peas, a variety with very small seeds, are much cultivated in France and Germany, being sown in October, enduring the severest frosts without injury, and ripening very early.
Besides being one of its most important agricultural and horticultural crops, peas are largely imported into Britain, the quantity sometimes reaching 120,000 quarters. The chief sources are Denmark, Germany, Holland, Morocco, the United States, British North America; and of these Denmark and the North American colonies send the greater part. As an article of food, if not taken too often or without other food, peas are very valuable, as they contain a large percentage of casein, which is a flesh-forming principle. This principle in the pea has been called legumin, but chemists are now generally agreed that it is identical with the casein of cheese. The chemical constituents of peas will be found in the table at DIET, Vol. III. p. 808; and the dietetic value is discussed at FOOD, Vol. IV. p. 719. Tinned peas are much used, but have little of the delightful flavour of this fresh vegetable.
A plant found on some parts of the shores of Britain, as well as of continental Europe and North America, and known as the Sea Pea, has been commonly referred to the genus Pisum, and called P. maritimum, although botanists now generally refer it to Lathyrus. It much resembles the common pea; has large reddish or purple flowers on many-flowered stalks; and its seeds have a disagreeable bitter taste. Its abundance on the sea-coast at Aldeburgh and Orford, in Suffolk, is said to have saved many persons from death by famine in 1555.—The other species of Pisum are few. But the name Pea is often given to species of other papilionaceous genera. The Sweet Pea (q.v.) and Everlasting Pea are species of Lathyrus. The Chick Pea (q.v.) is a species of Cicer; and the Wood or Heath Pea is Orobus tuberosus.—The pods of peas are often injured by the Pea-beetle (Bruchus pisi), a small coleopterous insect; by the Pea-maggot, the caterpillar of a moth (Tortrix pisi); and by the Pea-weevils (Sitona crinita and S. lineata), small coleopterous insects.