Table of Contents
Brigham, R.D. 1993. Castor: Return of an old crop. p.
380-383. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.
Castor: Return of an Old Crop
Raymond D. Brigham
- HISTORY OF PRODUCTION IN THE UNITED STATES
- THE PLANT
- Cultural Practices
- INSECTS AND DISEASES
- NEEDS AND FUTURE PROSPECTS
Production of castor (Ricinus communis L., Euphorbiaceae) is needed in
the United States to supply castor oil for the hundreds of products using this
versatile chemurgic raw material. Forty to 45 thousand tonnes of castor oil
and derivatives are imported each year (Roetheli et al. 1991) to supply the
entire needs of our domestic industries. The United States is the largest
importer and consumer of castor oil in the world. Castor oil is classed as a
strategic material critical to our national defense by the Agricultural
Materials Act P.L. 98-284 passed by Congress in 1984. Other "strategic"
materials include natural rubber and sperm whale oil substitutes. Public Law
81-774 requires that sufficient supplies of these materials be acquired and
stored in the United States to meet national defense needs in case of war
(Roetheli et al. 1991).
Castor was in production as early as the mid-1850s in the central part of the
United States, and over 23 crushing mills reportedly were operational at that
time (Zimmerman 1958). Sporadic production caused mills to eventually locate
on the east and west coasts to crush imported seed. In the mid-1930s, Baker
Castor Oil Company began a program to develop domestic production to supply
their processing plant in California. Contracts were offered to growers, and
limited production developed in the Imperial and San Joaquin Valleys (Zimmerman
1958). During World Wars I and II, domestic production was encouraged because
of castor oil's strategic value. Derivatives of castor oil are key ingredients
in hydraulic fluids, greases, and lubricants for military equipment. During
the Korean conflict, castor production was stimulated by a government sponsored
procurement program. The production area reached over 20,000 ha in 1951,
mainly in Texas, Oklahoma, California, and Arizona. Improved cultivars and
harvesting equipment allowed the crop to compete favorably with other field
crops. By 1959, Texas became the leading producer of castor, and production
was centered near Plainview (Brigham and Spears 1961). In the late 1960s, over
30,000 ha were grown in Texas. The seed was shipped to the crushing facility
of Baker Castor Oil Company, Bayonne, New Jersey. A small crushing facility
with solvent extraction was built in Plainview in the early 1960s by the Plains
Cooperative Oil Mill of Lubbock. This plant operated until castor production
ceased in the early 1970s. Castor production and processing was discontinued
due to: (1) low world prices for castor oil; (2) higher prices being paid for
competing crops grown in the High Plains area; (3) the cooperative oil mill and
castor oil buyers not agreeing on a contract price for the oil in 1972, and (4)
elimination of the government price support for castor in 1972. Since that
time, only limited plantings for seed production have been made. Some planting
seed of the cultivar 'Hale' was exported to other countries during the 1980s.
Although commonly referred to as a "bean," castor is not a legume. The plant
has also been called the "castor oil plant." Castor oil, one of the oldest
commercial products, was used in lamps by the Egyptians more than 4,000 years
ago, and seeds have been found in their ancient tombs (Weiss 1971). Castor is
considered by most authorities to be native to tropical Africa, and may have
originated in Abyssinia (Weiss 1971).
Although grown as annual plants, they act as perennials in the tropics and
subtropics and the plants reach heights of 9 to 12 m. The dwarf-internode
cultivars 'Hale' and 'Lynn', and hybrids using them as the pollen parent, vary
in height from 0.9 to 1.5 m, compared to 1.8 to 3.7 m for the normal-internode
types formerly grown (Brigham 1970a,b). Soil conditions, availability of
moisture, and levels of nutrients can cause considerable variation in height of
plants. Plants have a tap root, plus prominent lateral roots below the soil
The large leaves are palmately lobed, (hence the name Palma Christi used for
castor) and are borne more or less alternately on the stems, except for the two
opposite leaves at the node just above the two cotyledonary leaves. The
petioles are usually several times as long as the long axis of the leaves. The
main stem is terminated by the first or primary raceme, which often is the
largest on the plant. The primary raceme of early dwarf-internode cultivars
usually occurs after the 6th to 10th node. On later cultivars, the primary
raceme may occur after the 8th to 16th node. In introductions from other
countries, dwarf-internode types flowering after 40 or more nodes are known.
After the first raceme appears, branches originate at the nodes below it. The
number of branches depends on plant spacing and in some cases the cultivar.
Under field conditions, two or three branches occur at almost the same time,
but generally in the following order: the first branch at the node immediately
beneath the primary raceme, the second at the second node, and the third at the
third node below the primary raceme. The first racemes formed on the branches
are commonly called the "second set" of racemes. Subsequent branches arise
from the nodes just beneath the racemes of the second set. This sequence of
development continues as long as the plant remains alive and growing actively.
Thus, the development of racemes along any one axis is sequential, making it
possible for a plant to have racemes in all stages of development from bud
stage to complete maturity.
Typically, the racemes usually bear pistillate flowers on the upper 30 to 50%
and staminate flowers on the lower 70 to 50% of the raceme. Number of
staminate and pistillate flowers can vary greatly, depending upon raceme size.
The flowers are without petals. After the pollen is shed, the staminate
flowers dry up and usually drop. The pollen, which is discharged forcibly from
the anthers, is carried to stigmas mainly by wind (Brigham 1967). After
fertilization, the pistillate flowers develop into spiny capsules, though
spineless types are known. At maturity, the hull (pericarp) of the capsule may
split along the outside seam (dorsal suture) of each of the three capsule
segments (carpels). If splitting is violent, as in wild types, the seed will
be ejected and scattered on the ground around the plant. This type of
splitting (dehiscence) is not present in cultivars grown for mechanized
production. Seeds of present cultivars are held within the capsule for several
weeks after frost with no appreciable loss.
Seeds of current cultivars weigh from 3.0 to 3.5 g. Seed color ranges from
light to dark brown, with various mottling patterns. The seed coat makes up
about 25% of the weight of the seed. Oil content averages 50% on a dry weight
Chromosome number of castor is 2n = 20. Autotetraploids have been
produced using colchicine, and haploids have been reported, but in nature,
castor is found mainly in the diploid form. There is little or no loss of
vigor when castor plants are inbred (Moshkin 1980).
Highest yields of castor are produced under irrigation on fine or medium
textured soils, and where low relative humidity prevails. Areas where soils
are infested with the cotton root-rot fungus should not be considered for
growing castor, because the plants are highly susceptible to this disease
(Brigham and Spears 1961). At least a 140-day growing season is required (from
planting until first killing frost) to produce satisfactory yields of castor
seed, and a 150 to 160-day season is more desirable.
Seedbed preparation is similar to cotton, maize, sorghum, soybean, and other
row crops. Deep tillage, such as chiseling 20 to 30 cm deep, encourages
development and deeper penetration of the tap root. Castor is usually planted
in a shallow furrow by opening a bed with a lister-type planter, or planting
can be on low beds. Beds usually are irrigated before planting by running
water down the furrows. Land should be prepared for 0.96 to 1.01 m rows to fit
the available harvesters.
Castor should be planted when the soil is warm--a 10 day average of 15.6°C
at 20 cm depth at 8 a.m. In the Plainview, Texas, area, May 5 to 25 is usually
satisfactory. Castor should not be planted after June 10 in that area. Only
seed of high germination and of good quality should be planted to assure timely
emergence and adequate plant populations. Seed treatment materials may be
applied if needed to control damping-off in cold soils.
Castor seeds are large and slow to germinate; emergence of the seedlings may
take 7 to 14 days. Castor seeds require moist soil over a longer period than
maize or cotton. Seeds should be planted 6.3 to 7.6 cm deep, depending on
texture and condition of the soil. If press wheels are used in contact with
the seed, care should be taken that they do not crush the seed. Castor is
planted in 0.96 to 1.01 m rows, with a seeding rate of 11.2 to 15.7 kg/ha and
plant spacing of 20 to 25 cm within the row. Special care must be taken to
prevent crushing the fragile seed in the planter box. Air planters are ideal,
and can space seeds precisely. Use of an inclined-plate planter is also a
preferred method, but a cotton planter box can be used if properly modified
(Brigham and Spears 1961).
Adequate amounts of nitrogen, phosphorus, and potassium must be available to
produce high yields of castor seed. Levels of these nutrients should be
determined by soil test. If the soil is deficient in nitrogen, 90 to 135 kg/ha
of nitrogen usually are needed for maximum yields. A split application of
nitrogen is often used, with the second half sidedressed between the rows at
last cultivation. If phosphorus is needed, application should be made before
planting time. Potassium can be applied at planting time. A minimum of 37 to
56 kg/ha of P is needed for production of castor, and 15 to 19 kg/ha of K.
Where preplant furrow irrigation is applied, castor plants should not require
irrigation until the first racemes appear on the plant. Under normal
conditions, 12 to 14 days between irrigations should keep plants from stressing
for moisture, but high temperatures and high winds during the peak growing and
fruiting periods may cause the plants to need more frequent irrigation. Castor
requires 20.6 to 24.7 cm/ha of water annually to produce high yields. The time
of last irrigation is usually from 1 to 10 Sept.
Cultivation is much the same as for controlling weeds in cotton or soybeans.
Rotary hoes are often used before or after the plants emerge to control small
annual weeds and grasses. Cultivation with sweeps should be as shallow as
possible to prevent damage to the fibrous root system of the plants.
Trifluralin is labelled as a preplant incorporated herbicide for control of
certain broadleaf weeds and grasses.
The castor plant is not toxic to most insects, even though small amounts of the
toxic protein, ricin, and the alkaloid tricinine, occur in vegetative parts of
the plant (Weiss 1971). However, only infestations of false chinch bugs have
become serious enough to warrant control measures in the Texas High Plains, and
those occur only in a few fields every few years. Thrips, corn earworms,
armyworms, spider mites, leaf miners, lygus bugs, and green stink bugs have
been observed in castor fields with minimal damage.
Castor plants are attacked by numerous diseases under high relative humidity
conditions, but only a few occur in the High Plains area. Alternaria leaf
spot, caused by Alternaria ricini (Yoshii) Hansf., caused defoliation to
varying degrees of earlier susceptible cultivars, but later released cultivars
such as 'Hale' and 'Lynn' (Brigham 1970a,b) show resistance to this fungus.
Bacterial leaf spot, caused by Xanthomonas ricinicola (Elliott) Dowson,
also caused serious damage to susceptible cultivars, but the above
dwarf-internode cultivars have moderate resistance to bacterial leaf spot.
Gray mold, caused by Botryotinia ricini (Godfrey) Whetzel, has been
observed a few times in the Plainview area, but has never been considered a
problem. The organism causing cotton root rot, Phymatotrichopsis
omnivara (Duggar) Hennebert, attacks castor, and plants should not be grown
on infested soils. Charcoal rot, caused by Macrophomina phaseolina
(Tassi) Goidanich, has been observed on plants that were stressed for soil
moisture. Capsule mold, incited by a complex of fungi, causes capsules to stop
development and turn bluish-purple or brown to black. This only occurs after
high rainfall periods, so is usually not a problem on the High Plains. The
dwarf-internode castor cultivars are resistant to Verticillium wilt caused by
Verticillium species (Brigham and Minton 1969).
Dwarf-internode castor plants are usually ready to harvest about 10 days after
a killing frost, if normal drying weather prevails. Capsules should be dry
enough for the seed to hull when rubbed between the hands (Schoenleber 1961).
The newest harvester has a 4-row header that uses rotating brushes to remove
the capsules from the plants. This harvester, adapted to a grain combine, uses
rubber-covered cylinders to hull the seed. Ground speed under favorable
conditions can be 8 km/hr. Relative humidity must be below 40% when harvesting
castor seed, and moisture content of the seed should be 6% or lower. Castor
seed stores well, and does not deteriorate significantly in storage for at
least 2 years.
Yields of irrigated castor range from 2,242 to 3,363 kg/ha, and some fields
have produced 3,811 to 4,035 kg/ha. The seed is usually bought at a price
directly related to the world market. There are no government acreage controls
or price support programs.
To restart domestic production, industries in the United States which are large
users of castor oil will need to make contractual agreements on the price to be
paid for oil which will attract both grower and processor. To encourage
sufficient production of castor seed to supply the castor oil needs of our
domestic industries the following factors need to be addressed:
If castor production can be stimulated and production can again be realized,
research priorities include:
- Grower contracts at a price which will attract hecterage now devoted to other
- Adequate supplies of high-quality planting seed of dwarf-internode,
open-pollinated cultivars or F1 hybrids.
- A sufficient number of special built harvesters to harvest the seed from plants
after a killing frost.
- A crushing/processing facility, dedicated to crushing castor seed, located in
the production area.
- A contractual agreement by the processor to market castor oil over a period of
- Bridge financing for seed inventory from the time seed is received at the plant
until oil is sold.
- Acceptance of the crop by growers and the agricultural community.
- Detoxification and deallergenation of castor meal to allow use in livestock
- Government programs with incentives to produce alternative crops not in
- Development of improved hybrids to increase yield and oil percentage of castor
- Development of breeding lines with improved disease and insect resistance,
drought tolerance, and shatter resistance.
- Mutagenesis and genetic research to eliminate ricin, the toxic seed protein.
- Acquisition and preservation of germplasm useful to a breeding program.
- Improvement of harvesters to more efficiently harvest and hull the seed.
- Investigation of more economical and efficient methods of oil extraction, such
as use of extruders.
- Brigham, R.D. 1967. Natural outcrossing in dwarf-internode castor, Ricinus
communis L. Crop Sci. 7:353-355.
- Brigham, R.D. 1970a. Registration of castor variety Hale. Crop Sci.
- Brigham, R.D. 1970b. Registration of castor variety Lynn. Crop Sci.
- Brigham, R.D. and E.B. Minton. 1969. Resistance of dwarf-internode castor
(Ricinus communis L.) to Verticillium wilt. Plant Dis. Rptr.
- Brigham, R.D. and B.R. Spears. 1961. Castorbeans in Texas. Texas Agr. Expt.
Sta. Bul. 954.
- Moshkin, V.A. 1980. Castor. Kolos Publishers, Moscow. (English translation
by American Publishing Co. Pvt. Ltd., New Delhi, 1986).
- Roetheli, J.C., L.K. Glaser, and R.D. Brigham. 1991. Castor: Assessing the
feasibility of U.S. production. Workshop summary, Plainview, TX, Sept. 18-19,
1990. USDA/CSRS Office of Agr. Materials. Growing Ind. Material Ser.
- Schoenleber, L.G. 1961. Mechanization of castorbean harvesting. Oklahoma
Agr. Expt. Sta. Bul. 591.
- Weiss, E.A. 1971. Castor, sesame, and safflower. Leonard Hill, London.
- Zimmerman, L.H. 1958. Castorbeans: a new crop for mechanized production.
Adv. Agron. X:257-288.
Last update April 21, 1997