1911 Encyclopædia Britannica/Pea

PEA (Pisum), a genus of the order Leguminosae, consisting of herbs with compound pinnate leaves ending in tendrils, by means of which the weak stems are enabled to support themselves, and with large leafy stipules at the base. The flowers (fig. 1) are typically “papilionaceous,” with a “standard” or large petal above, two side petals or wings, and two front petals below forming the keel. The stamens are ten—nine united, the tenth usually free or only slightly joined to the others.

Flower of Pea.

Fig. 1.—Flower of Pea.

 c, Calyx.
 st, Standard.
 a, Alae, or wings
 car, Carina, or Keel.

This separation allows approach to the honey which is secreted at the base of the staminal tube. The ovary is prolonged into a long, thick, bent style, compressed from side to side at the tip and fringed with hairs. The fruit is a characteristic "legume" or pod (fig. 2), bursting when ripe into halves, which bear the large globular seeds (peas) on their edges. These seeds are on short stalks, the upper extremity of which is dilated into a shallow cup (aril), the two seed-leaves (cotyledons) are thick and fleshy, with a radicle bent along their edges on one side. The genus is exceedingly close to Lathyrus, being only distinguished technically by the style, which in the latter genus is compressed from above downwards and not thick. It is not surprising, therefore, that under the general name “pea” species both of Pisum and of Lathyrus are included. The common field pea with tan-coloured or compressed mottled seeds and two to four leaflets is Pisum arvense, which is cultivated in all temperate parts of the globe, but which, according to the Italian botanists, is truly a native of central and southern Italy: it has purple flowers. The garden pea, P. sativum, which has white flowers, is more tender than the preceding, and its origin is not known. It has not been found in a wild state anywhere, and it is considered that it may be a form of P. arvense, having, however, from four to six leaflets to each leaf and globular seeds of uniform colour.

The Pod (legume) of the Pea.

From Vine’s Students’ Text book of Botany, by permission of Swan, Sonnenschein & Co.

Fig. 2—The Pod (legume) of the Pea.
r, The dorsal suture.
b, The ventral.
c, Calyx.
s, Seeds.

P. sativum was known to Theophrastus; and De Candolle (Origin of Cultivated Plants, p. 329) points out that the word "pison" or its equivalent occurs in the Albanian tongue as well as in Latin, whence he concludes that the pea was known to the Aryans, and was perhaps brought by them into Greece and Italy. Peas have been found in the Swiss lake-dwellings of the bronze period. The garden peas differ considerably in size, shape of pod, degree of productiveness, form and colour of seed, &c. The sugar peas are those in which the inner lining of the pod is very thin instead of being somewhat horny, so that the whole pod can be eaten. Unlike most papilionaceous plants, peaflowers are perfectly fertile without the aid of insects, and thus do not intercross so freely as most similar plants do. On the other hand, a case is known wherein the pollen from a purple-podded pea applied to the stigma of one of the green-podded sugar peas produced a purple pod, showing that not only the ovule but even the ovary was affected by the cross. The numerous varieties of peas in cultivation have been obtained by cross-fertilization, but chiefly by selection. Peas constitute a highly nutritious article of diet from the large quantity of nitrogenous materials they contain in addition to starchy and saccharine matters.

The sweet pea, cultivated for the beauty and fragrance of its flowers, is a species of the allied genus Lathyrus (L. odoratus), a native of southern Europe. The chick pea (q.v.) (Cicer arietinum), not cultivated in England, is still farther removed from the true peas. The everlasting pea of gardens is a species of Lathyrus (L latifolius) with very deep fleshy roots, bold foliage, and beautiful but scentless flowers; the field pea (Pisum arvense) is better adapted than the bean to light soils, and is best cultivated in rows of such a width as to admit of horse-hoeing. The early stage at which the plants fall over, and forbid further culture, renders it even more needful than in the case of beans to sow them only on land already clean. If annual weeds can be kept in check until the peas once get a close cover, they then occupy the ground so completely that nothing else can live under them; and the ground, after their removal, is found in the choicest condition. A thin crop of peas should never be allowed to stand, as the land is sure to get perfectly wild. The difficulty of getting this crop well harvested renders it peculiarly advisable to sow only the early varieties.

The pea prefers a friable calcareous loam, deeply worked, and well enriched with good hotbed or farm-yard manure. The early crops require a warm sheltered situation, but the later are better grown 6 or 8 ft. apart, or more, in the open quarters, dwarf crops being introduced between the rows. The dwarf or early sorts may be sown 3 or 4 ft. apart. The deep working of the soil is of importance, lest the plants should suffer in hot dry weather from mildew or arrest of growth. The first sowing may be made about the beginning or middle of November, in front of a south wall, the plants being defended by spruce fir branches or other spray throughout the winter. In February sowings are sometimes made in private gardens, in flowerpots or boxes, and the young plants afterwards planted out. The main crop should be sown towards the end of February, and moderate sowings should be made twice a month afterwards, up to the beginning of July for the north, and about the third week in July for warmer districts. During dry hot weather late peas derive great benefit from mulching and watering. The latest sowings, at the middle or end of August, should consist of the best early sorts, as they are not so long in producing pods as the larger and finer sorts, and by this means the supply may be prolonged till October or November. As they grow the earth is drawn up to the stems, which are also supported by stakes, a practice which in a well-kept garden is always advisable, although it is said that the early varieties arrive sooner at maturity when recumbent.

Peas grown late in autumn are subject to mildew, to obviate which it has been proposed to dig over the ground in the usual way, and to soak the spaces to be occupied by the rows of peas thoroughly with water—the earth on each side to be then collected so as to form ridges 7 or 8 in. high, these ridges being well watered, and the seed sown on them in single rows. If dry weather at any time set in, water should be supplied profusely once a week.

To produce very early crops the French market-gardeners used to sow early in November, in frames, on a border having a good aspect. the seeds being covered very slightly. The young plants are transplanted into other frames in December, the ground inside being dug out so as to be 18 or 20 in. below the sashes, and the earth thus removed placed against the outside of the frames. The young plants, when 3 or 4 in. high, are planted in patches of three or four, 8 in. asunder, in four longitudinal rows. The sashes are covered at night with straw mats, and opened whenever the weather is sufficiently mild. When 8 or 10 in. high the stems are inclined towards the back of the frame, a little earth being drawn to their base, and when the plants come into blossom the tops are pinched out above the third or fourth flower to force them into bearing. As soon as they begin to pod, the soil may have a gentle watering, whenever sufficiently warmed by the sun, but a too vigorous growth at an earlier period would be detrimental. Thus treated the plants bear pods fit for gathering in the first fortnight in April.

A very convenient means of obtaining an early crop is to sow in 5-in. pots, a few seeds in each, the plants to be ultimately planted out on a warm border Peas may also be obtained early if gently forced in frames, in the same way as kidney beans, the dwarfest varieties being preferable.

For the very early peas the rows should range east and west, but for the main crops north and south. The average depth of the drills should be about 2 in. for small sorts, and a trifle more for the larger kinds The drills should be made wide and flat at bottom so that the seeds may be better separated in sowing. The large sorts are the better for being sown 3 in. apart Chopped furze may be advantageously scattered in the drill before covering in, to check the depredations of mice, and before levelling the surface the soil should be gently trodden down over the seeds.

A good selection of sorts may be made from the following:—

Early.—William Hurst; Chelsea Gem; Sutton’s Bountiful and Excelsior, Gradus.

Second Early.—Stratagem; Telephone; Telegraph; Carter’s Daisy; Duke of York; Veitch’s Autocrat.

Late.—Veitch’s Perfection; Ne Plus Ultra, the finest of all late peas, but a little delicate in cold wet soils and seasons; British Queen; Champion of England; Duke of Albany.