The castor-oil plant or Palma Christi (Ricinus communis) is a robust perennial in tropical countries which becomes an annual in regions subject to frost. The seeds of this plant, called "castor beans" or "mole beans," yield the castor oil of commerce. Between 1860 and 1900, the castor bean was an important crop in certain sections of Oklahoma, Kansas, Missouri, and Illinois, but during recent years its culture has been practically abandoned in favor of crops which are easier to handle and more profitable.

For the commercial production of castor beans a warm climate and long growing season are necessary. If planted much farther north than St. Louis, Mo., or Washington, D. C, the crop is very likely to be caught by frost. In general, any fertile soil which produces good crops of cotton or corn is suitable for castor beans, but a very fertile soil favors the growth of the plant at the expense of seed production and early maturity. The land is prepared in much the same manner as for cotton or corn; that is, plowed, disked, and harrowed level before planting, which may be done by hand or with a corn planter with specially prepared plates. The seed should be planted early in the spring, as soon as the soil is warm but still moderately moist. The time of planting varies according to locality, but in general corresponds to that of cotton.

The seed is planted in hills at a depth of 1 to 2 inches. Toward the north, the rows are usually made 4 feet apart and the hills spaced 3 feet apart in the row. Farther south the rows should usually be made about 6 to 8 feet apart. On very light land the hills may be 4 feet apart in the row; on heavier land, 6 to 8 feet apart. As a general rule three seeds are planted to the hill, and not less than two should be planted. One bushel of medium-sized seed should plant from 5 to 6 acres. When the plants are from 4 to 6 inches tall, the weaker ones should be removed, leaving one plant in a hill.

The crop is cultivated similar to corn until the plants are large enough to shade the ground. In case the field becomes foul with weeds and grass, some hoeing may be necessary, but practically all the cultivation required can be done with a horse-drawn weeder. Some varieties in which the beans pop out when the hull is fully ripe are known locally as "poppers," and after the beans begin to ripen, the field must be gone over every few days and the ripe beans collected in order to avoid loss. Other varieties tend to retain the beans in the hull after they are ripe. The climate affects the popping of the beans, and a variety which shatters badly in one region may shatter very little when grown in another.

In harvesting, a common method is to cut off the spikes with a knife and collect them in large sacks. They are then hauled to a shelter of some kind and allowed to dry until the pods will crush easily. Various methods are used in thrashing castor beans. If the variety grown is one which "pops" or drops its seeds when they are ripe, the spikes are sometimes piled on a hard ground or plank floor fully exposed to the sun and furnished with sides of boards or cloth 6 to 8 feet high to catch the beans as they pop out. In some varieties mere drying does not cause the pods to open, and specially constructed machines have been used to remove the beans from the pods. After the beans have been thrashed or popped out, a fanning mill is used to separate the hulls, chaff, and dirt from the beans, which are then sacked and stored for market.

The yield varies greatly and will depend much upon cultural conditions, the season, the variety grown, and the care exercised in harvesting and thrashing the seeds. In Oklahoma the average yield of the popping varieties is said to be 8 to 10 bushels per acre. Yields up to 25 bushels per acre have been reported for favorable conditions.

For some years prior to the war the farm price for castor beans was about $1 a bushel. Early in the war the increased demand for castor oil caused a sharp advance in the price of the beans, which has gradually declined. In June, 1920, the wholesale market quotation was about $3 a bushel. The normal market requirement in the United States for castor beans is about 1,000,000 bushels annually, but during the last year of the war nearly 3,000,000 bushels were imported.

In the United States castor beans are used in quantity only by manufacturers of castor oil. In general, the equipment and operation of a castor-oil mill resembles that of a cottonseed-oil mill or linseed-oil mill, but special and expensive equipment is necessary for the proper extraction of the oil from castor beans. The best grade of oil is obtained from the beans by hydraulic pressure. An additional quantity of oil of lower grade is obtained by treating the press cake with naphtha or some other volatile solvent. The pomace resulting from the second extraction is used as a fertilizer for tobacco, corn, and other crops, but because of a poisonous principle can not be used for cattle feeding unless specially treated.

Owing to the heavy outlay required for the necessary machinery and the high cost of manufacture on a small scale, it has not been found profitable for the growers of castor beans to undertake the extraction of the oil.

The castor-oil plant is not known to be poisonous, and although the leaves are not relished by farm animals they are said to be used as fodder for cattle in India. Castor beans, however, contain a poisonous principle, and though harmless when handled, may cause serious if not fatal effects when eaten, especially in the case of small children. Care should be taken to prevent these beans from being accidentally mixed with the grain fed to animals, since many cases have been reported in which the death of horses has been due to eating feed in which they have become mixed.