Calotropis procera (Ait.) Ait. f. giant milkweed
Synonym: Asclepias procera Ait.
General Description.—Giant milkweed is also
known as sodom apple, calotrope, French cotton,
small crown flower (English), algodón de seda,
bomba (Spanish), cotton-france, arbre de soie, and
bois canon (French) (Howard 1989, Liogier 1995,
Neal 1965, Parrotta 2001).
This plant is a soft-wooded, evergreen,
perennial shrub. It has one or a few stems, few
branches, and relatively few leaves, mostly
concentrated near the growing tip. The bark is
corky, furrowed, and light gray. A copious white
sap flows whenever stems or leaves are cut. Giant
milkweed has a very deep, stout taproot with few
or no near-surface lateral roots. Giant milkweed
roots were found to have few branches and reach
depths of 1.7 to 3.0 m in Indian sandy desert soils
(Sharma 1968). The opposite leaves are oblongobovate
to nearly orbicular, short-pointed to blunt
at the apex and have very short petioles below a
nearly clasping, heart-shaped base. The leaf blades
are light to dark green with nearly white veins.
They are 7 to 18 cm long and 5 to 13 cm broad,
slightly leathery, and have a fine coat of soft hairs
that rub off. The flower clusters are umbelliform
cymes that grow at or near the ends of twigs. The
flowers are shallowly campanulate with five sepals
that are 4 to 5 mm long, fleshy and variable in
color from white to pink, often spotted or tinged
with purple. The fruits are inflated, obliquely
ovoid follicles that split and invert when mature to
release flat, brown seeds with a tuft of white hairs
at one end (Howard 1989, Liogier 1995, Little and
Range.—Giant milkweed is native to West Africa
as far south as Angola, North and East Africa,
Madagascar, the Arabian Peninsula, southern Asia,
and Indochina to Malaysia (Rahman and Wilcock
1991). The species is now naturalized in Australia,
many Pacific islands, Mexico, Central and South
America, and the Caribbean islands.
Ecology.—Giant milkweed favors open habitat
with little competition. This condition is most
completely met in overgrazed pastures and
rangeland. Other common habitats are beachfront
dunes, roadsides, and disturbed urban lots. The
species grows in dry habitat (150 to 1000 mm
precipitation) and sometimes in excessively
drained soils in areas with as much as 2000 mm of
annual precipitation. Giant milkweed may be
found in areas up to 1,000 m in elevation in India
(Parrotta 2001). It roots very deeply and rarely
grows in soils that are shallow over unfractured
rock. Soils of all textures and derived from most
parent materials are tolerated, as well as soils with
high sodium saturation. Beachfront salt spray is
not detrimental. Competition with tall weeds,
brush, and especially grass weakens existing
plants, and being overtopped and shaded by trees
soon eliminates them. During droughts in Puerto
Rico, giant milkweed is attacked by the orange
aphid, Aphis nerii Boyer de Fonscolombe, which
causes defoliation, death of branches, and aborted
fruits (Little and others 1974).
Reproduction.—Flowering and fruiting takes
place throughout the year (Little and others 1974).
Hundreds to thousands of seeds may be produced
per plant each year. The seeds in a Puerto Rican
collection averaged 0.0095 + 0.0027 g/seed or
about 100,000 seeds/kg (author’s observation).
Eighty-nine percent germination took place in
potting mix between 7 and 64 days after sowing.
Half the seed weight was found in the wing (silk).
The seeds are dispersed by wind and may fly for
several hundred yards in gentle breezes. Seedlings
may arise in abundance after rainy periods, but
only a few survive the first season. Using the
reserves in its large taproot, giant milkweed can
resprout year after year when burned or cut.
Growth and Management.—Giant milkweed
usually reaches heights of about 2 m, but may
occasionally reach 5 m in height and stem
diameters of 25 cm (Little and others 1974).
Growth is about 1 m the first year after sprouting
in Puerto Rico. Senescence of individual stems
takes place in about 5 years, but plants often
resprout afterwards. Giant milkweed does not form
dense stands, normally occurring as scattered
individuals. It can be a serious weed in pastures,
overgrazed rangelands, and poorly managed hay
fields. Although it probably is not possible to
eliminate existing stands through management
without ceasing grazing and harvest, it may be
possible to prevent their establishment. Some form
of chemical control would seem to be the only
practical option for eliminating existing stands but
no specific guidelines are available. Establishing
giant milkweed has been advocated for
environmental protection and as a nurse crop for
more valuable species (Campolucci and Paolini
1990). This can be done easily by planting
containerized seedlings or rooted cuttings.
Benefits.—Giant milkweed tissues, especially the
root bark, are used to treat a variety of illness
including leprosy, fever, menorrhagia, malaria,
and snake bite (Parrotta 2001). The latex is toxic
and can cause blisters and rash in sensitive
persons. The plant is occasionally grown as an
ornamental in dry or coastal areas because it is
handsome, of a convenient size, and is easy to
propagate and manage. It is recommended as a
host plant for butterflies (Mikula 2001). In the
past, the silky hairs were used to stuff pillows
(Little and others 1974). Giant milkweed was
tested as a host for sandalwood, Santalum album
L., a partial root parasite. It resulted in greater
growth of sandalwood than all other species tested
(Shinde and others 1993). Extracts, chopped
leaves, and latex have shown great promise as
nematicides, in vitro and in vivo (Anver and Alam
1992, Charu and Trivedi 1997). Sheep, goats, and
camels will eat the leaves of giant milkweed
during droughts, but consumption is low. If the
leaves are chopped and mixed with other feed,
consumption greatly increases with no ill effects.
(Abbas and others 1992, Nehra and others 1987).
Shade-dried giant milkweed leaves contained 94.6
percent dry matter, 20.9 percent ash, 19.6 percent
crude protein, 2.2 percent fat, 43.6 percent acid
detergent fiber, and 19.5 percent neutral detergent
fiber (Abbas and others 1992). Although it is
lightweight, the wood is used in impoverished
desert areas for a cooking fuel (Varshney and Bhoi
Abbas, B., A.E. El Tayeb, and Y.R. Sulleiman.
1992. Calotropis procera: feed potential for arid
zones. Veterinary Record 131(6): 132.
Anver, S. and M.M. Alam. 1992. Effect of latex
seed dressing on interacting root-knot and
reniform nematodes. Afro-Asian Journal of
Nematology 2: 1-2, 17-20.
Campolucci, P. and C. Paolini. 1990.
Desertification control in the Sahel regions—
low-cost large-scale afforestation techniques.
Note Tecniche 10. Centro di Sperimentazione
Agricola e Forestale di Sperimentazione per la
Pioppicoltura. 24 p.
Charu-Jain and P.C. Trivedi. 1997. Nematicidal
activity of certain plants against root-knot
nematode, Meloidogyne incognita, infecting
chickpea, Cicer arietinum. Annals of Plant
Protection Sciences 5(2): 171-174.
Howard, R.A. 1989. Flora of the Lesser Antilles,
Leeward and Windward Islands.
Dicotyledoneae. Part 3. Vol. 6. Arnold
Arboretum, Harvard University, Jamaica Plain,
MA. 658 p.
Liogier, H.A. 1995. Descriptive flora of Puerto
Rico and adjacent islands. Vol. 4. Editorial
de la Universidad de Puerto Rico, San Juan, PR.
Little, E.L., Jr., R.O. Woodbury, and F.H.
Wadsworth. 1974. Trees of Puerto Rico and the
Virgin Islands. Vol. 2. Agriculture Handbook
449. U.S. Department of Agriculture,
Washingtion, DC. 1,024 p.
Mikula, R. 2001. Butterfly plants for your garden.
tterflyplants.html. 5 p.
Neal, M.C. 1965. In gardens of Hawaii. Special
Publication 50. Bernice P. Bishop Museum
Press, Honolulu, HI. 924 p.
Nehra, O.P., M.C. Oswal, and A.S. Faroda. 1987.
Management of fodder trees in Haryana. Indian
Farming 37(3): 31, 33.
Parrotta, J.A. 2001. Healing plants of Peninsular
India. CAB International, Wallingford, UK and
New York. 944 p.
Rahman, M.A. and C.C. Wilcock. 1991. A
taxonomic revision of Calotropis
(Asclepiadaceae). Nordic Journal of Botany
Sharma, B.M. 1968. Root systems of some desert
plants in Churu, Rajasthan. Indian Forester
Shinde, S.R., R.D. Ghatge, and S.S. Mehetre. 1993.
Comparative studies on the growth and
development of sandalwood tree in association
with different hosts. Indian Journal of Forestry
Varshney, A.C., and K.L. Bhoi. 1988. Cloth from
bast fibre of the Calotropis procera (aak) plant.
Biological wastes 26(3): 229-232.
John K. Francis, Research Forester, U.S.
Department of Agriculture, Forest Service,
International Institute of Tropical Forestry, Jardín
Botánico Sur, 1201 Calle Ceiba, San Juan PR
00926-1119, in cooperation with the University of
Puerto Rico, Río Piedras, PR 00936-4984