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.