Stranglers & Banyans

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Noteworthy Plants For October 1999

Stranglers and Banyans

Amazing Figs Of The Tropical Rain Forest

Of all the trees on earth, the figs (Ficus) certainly have the most bizarre growth forms and the most ingenious method of pollination. Imagine a tree with numerous snakelike, aerial roots growing downward from the limbs, a massive, buttressed trunk with huge surface roots spreading in all directions, and a peculiar aggressive growth habit that literally strangles other trees. Although most people are familiar with the Old World edible fig (F. carica), the vast majority of fig species grow wild in exotic tropical regions of the world. Their unmistakable growth form resembles the background scenery from a "Tarzan" or "Rambo" movie. Several unusual species were planted in Florida and southern California near the turn of the century, and include some of the most spectacular trees in parks and botanical gardens. Unfortunately, some of these introduced species have proved to be a nuisance in humid regions of the United States.

Although not considered a strangler, the creeping fig (Ficus pumila) of eastern Asia can completely envelop a four-story building if not trimmed regularly. The new juvenile growth (top) has smaller leaves. The syconium is lined with all long-style female flowers. Without pollen-bearing male plants with fig wasps, no seeds can be produced and this plant must be propagated by cuttings.

The genus Ficus, a member of the diverse Mulberry family (Moraceae), is one of the largest genera of woody flowering plants with approximately 1,000 different species. It is rivaled in size by only a few other genera of trees and shrubs, such as Acacia (800), Eucalyptus (500), and Cassia (500). With the exception of the Hawaiian Islands, practically every tropical continent and major island group has one or more indigenous (native) species of fig. In fact, the tiny island of Barro Colorado, located in the Panama Canal Zone, has 17 native species. This is remarkable considering that the island has an area of only six square miles. Even more remarkable, virtually every fig species has its own unique species of "in house" wasp pollinator. The wasps are housed throughout the year inside the fig's hollow fruits (called syconia)--in one of nature's most amazing symbiotic relationships between a tree and an insect. The symbiotic wasps undoubtedly play a major role in the ability of different fig species to grow in the same locality, a phenomenon known as "species packing."

Fig and Fig Wasp Symbiosis:

  The Calimyrna Fig And Its Pollinator Wasp
  Figs Of The Holy Land (Their Role In Religions)
  Gall Controversy: Are Galls Induced By Fig Wasps
  Evolution and Pollination Patterns In Dioecious Figs
  Sex Determination In The Common Fig (Ficus carica)
  Fig Sexuality: Plant Sexuality & Political Correctness
  The Amazing Fig and Fig Wasp Symbiotic Relationship

In their native tropical habitats, many figs are called "stranglers." Seeds germinate high on the moist branches of rain forest trees, sending numerous aerial roots to the ground. The sticky seeds are dispersed by a variety of fruit-eating birds and bats. Like botanical boa constrictors the serpentine roots gradually wrap around the host's limbs and trunk, crushing the bark and constricting vital phloem and cambial layers. The network of roots, resembling a tangle of writhing snakes, also fuse together (anastomose) forming a massive woody envelope or "straightjacket" encircling the host. Expansion of the host trunk as it grows in girth may accentuate the death grip and subsequent girdling process. Eventually the host tree dies of strangulation and shading, and the strangler fig stands in its place. In many cases the host tree may actually succumb from shading and root competition rather than strangulation. When strangler figs start in the ground, as in cultivation, their trunks develop from the ground upward like other "conventional" trees.


A: The vinelike aerial roots of a strangler fig (Ficus citrifolia) draped around the trunk of a mamme apple (Mammea americana) on the island of St. John, U.S. Virgin Islands.

B: Like a giant botanical boa constrictor, this strangler fig (Ficus aurea) is wrapped around the trunk of a cabbage palm (Sabal palmetto) in the Florida Everglades.

Several exotic fig species, such as the commonly cultivated Benjamin fig (Ficus benjamina), Indian laurel fig (F. microcarpa), rustyleaf fig (F. rubiginosa), and Moreton Bay fig (F. macrophylla), often develop as stranglers with numerous aerial roots in their native habitats of Malaysia and tropical Australia. Due to the introduction of wasp pollinators, some of these commonly-grown strangler figs in southern California produce viable seeds. They sometimes germinate in the crowns of palms and in crevices of buildings; however, it is generally too arid for them to send aerial roots to the ground and develop epiphytically.

An unusual sight on the campus of Palomar College in San Diego County, California: A healthy rustyleaf fig (Ficus rubiginosa) that has developed from a seed in the leaf bases of a Canary Island date palm (Phoenix canariensis). If the climate were more humid, with frequent rain showers, this fig could probably send aerial roots to the ground and become a full-fledged strangler. In fact, small aerial roots (not visible in photo) were already developing on the underside of the main stem.

The colorful syconia of Ficus mysorensis in the Palomar College Arboretum. This is a strangler fig native to tropical Asia. The syconia are lined on the inside with minute male and female flowers. The female flowers are pollinated by a tiny symbiotic wasp.

In humid southern Florida, several species of Asiatic strangler figs commonly develop epiphytically with numerous aerial roots. The symbiotic wasp pollinators have also been introduced in Florida for these exotic figs resulting in prolific seed production. As with many other naturalized alien plants, the original gardeners probably didn't realize that their "harmless" plantings would eventually pose a threat to valuable cultivated and native plants. Much to the chagrin of citrus growers, several exotic strangler figs have now attacked orange and grapefruit trees. In addition, two native Florida strangler figs (Ficus aurea and F. citrifolia) commonly attack palms, bald cypress, oaks and many other trees in the Everglades and Keys. Due to the lack of an outer cambial and phloem layer, palms can generally survive the death grip of a strangler fig--that is until they are gradually shaded out.


A: A striking example of a strangler fig (Ficus aurea) that has completely engulfed the trunk of a cabbage palm (Sabal palmetto) in the Florida Everglades.

B: A strangler fig (Ficus aurea) tightly wrapped around the trunk of a bald cypress (Taxodium distichum) in the Florida Everglades. Although the bald cypress appears to be relatively unharmed at this stage, its trunk is becoming deeply indented due to the powerful aerial roots of the fig.

Florida strangler figs also wrap around masonry walls and other stationary objects, including historic East Martello Museum near Key West Airport. The original structure was East Martello Tower, a study brick fortress constructed in 1862 during the Civil War period. One crumbling old brick wall in downtown Key West is actually being held together by a network of fig roots. Throughout Key West, fig seedlings germinate readily in cracks and crevices of old buildings, gradually sending a weblike mass of aerial roots down the walls to the ground. Some residents of the Coral Gables area consider the Asiatic banyan-type figs to be a nuisance and potential menace. The massive, spreading roots of these enormous trees buckle pavement and concrete swimming pools, plug drainage and sewer lines, and pose a serious threat to underground utilities.

This Asian strangler fig (probably Ficus altissima) has enveloped a masonry wall in Coral Gables, Florida.

The tentacle-like aerial roots of a strangler fig (Ficus citrifolia) on the Island of Dominica in the Lesser Antilles. Like a giant "vegetable octopus" they have reduced this 19th century block wall at the Commandant's Quarters at Fort Shirley to rubble.

Aerial roots of the strangler fig (Ficus citrifolia) wrapped around the trunk and limbs of a swamp tree called "wing-nut" (Pterocarpus officinalis) on the island of Dominica. In fact, the Caribbean island of Barbados is apparently named for this species of strangler fig whose abundant aerial roots give it a "bearded" appearance.

Strangler figs are common throughout the Caribbean and tropical Americas. In fact, the island of Barbados is supposedly named for a common strangler fig (Ficus citrifolia), whose abundant aerial roots often give it a "bearded" appearance. Occasionally, a strangler fig wrapped around the trunk of a palm is washed ashore on a Caribbean beach, evidence of the powerful forces of hurricanes that sweep across this region each summer and fall. The names "higuero" and "higueron" as well as "matapalo" (tree-killer) are commonly given to the wild figs, but in more general use in Central America is the term "amate." Both Aztecs and Mayans used bark from native strangler figs to make a kind of paper for the original Mexican codices. The paper was called amatl in Nahuatl and copo in Mayan. Thin strips of bark were pounded with a stone until a sheet of paper resulted, a process not unlike the production of papyrus paper by Egyptians. Fig trees are mentioned in poetry and romance of Central America, and the trees have become intimately associated with daily life and are regarded with affection. The amate is called the national tree in El Salvador. Village markets are often held in the ample shade of a giant fig tree or a huge kapok (Ceiba pentandra).

Strangler fig (possibly Ficus aurea) wrapped around palm trunk that was washed ashore on the island of Grand Cayman. Photo by Harriett Feeney.

In Yucatan and Central America, strangler figs are an important component of the tropical forest, providing food and habitats for a variety of animal species. According to Paul C. Standley (Flora of Yucatan, 1930), they are also a major factor in the destruction of Mayan cities. Seeds dispersed by fruit-eating birds and bats germinate in crevices high on the walls of buildings. The powerful roots force their way between stone blocks, gradually reducing massive vertical walls to rubble. Many ancient cities still remain partially or completely covered by huge strangler figs and other vegetation. In Guatemala, the spectacular pyramids of Tikal resemble islands of stone in a verdant sea of tropical forest. A steep trail ascends one of the tallest pyramids, winding through a labyrinth of fig roots which serve as convenient steps and hand rails.

A strangler fig (Ficus cotinifolia) growing on a block wall at the ancient Maya city of Tulum in Yucatan, Mexico. Large strangler figs such as this have been a major factor in the demolition of these ancient cities made of limestone blocks.

The beautiful resort town of Cabo San Lucas in Baja California, has an unusual use for palm trunks enveloped by the snakelike roots of strangler figs. They are used as structural supports for palm-thatched palapas and as decorative pillars in plush hotels. In one deluxe condominium the palm trunks and strangler figs were beautifully finished with a high gloss varnish. They were undoubtedly imported from tropical Mexico, grim evidence of man's destructive effect on the tropical rain forest.

Although not a typical strangler, a native Baja California fig (Ficus palmeri) has seeds that germinate on vertical rock walls in remote canyons. Another similar species (F. petiolaris) grows in rugged arroyos and mountains of mainland Mexico. These unusual figs are undoubtedly isolated remnants from a widespread tropical flora that covered parts of Mexico during the Tertiary Period when Baja California was contiguous with the mainland. The seedlings of both species develop an unusual swollen (caudiciform) base containing water storage tissue. They survive prolonged periods of drought and then resume growth when water is available. In the Sierra de la Giganta in Baja California, numerous adventitious roots of F. palmeri grow down sheer rock walls, eventually fusing into a creamy white trunk resembling a cascading waterfall or lava flow made of wood. In the rugged Cape region, huge surface roots wrap around boulders like a giant vegetable octopus. The taxonomic status of another Baja California fig (F. brandegeei) awaits a comprehensive study of the pollinator wasps of these fascinating trees.

Ficus palmeri in Baja California

Ficus palmeri in Baja California. Left: Bahia Juncalito south of Loreto. Right: Sierra de la Laguna north of San Jose del Cabo. Note the numerous surface roots spreading outwardly in all directions. This same root pattern can be seen in the large Moreton Bay fig (Ficus macrophylla) near the San Diego Natural History Museum and in the Palomar College Arboretum.

  Moreton Bay Fig In Palomar College Arboretum  

Ficus palmeri in Baja California. Arroyo southwest of Loreto in foothills of Sierra de la Giganta. The gray trunk in left image appears to have melted and flowed down the steep rock face like an arboreal waterfall. Actually, adventitious (aerial) surface roots from the trunk grew down the canyon wall and fused together (anastomosed). The aerial roots of tropical banyans form pillar-like prop roots that support the massive, spreading limbs. In strangler figs of the rain forest the aerial roots wrap around host trees like botanical boa constrictors.

An enlarged view of the above Ficus palmeri near Loreto.

Clusia rosea: A Strangler That Is Not A Fig

The strangler habit is not limited to figs. The pitch apple (Clusia rosea) often develops epiphytically on other trees. In Virgin Islands National Park it is often called "strangler fig," but actually belongs to a different tropical plant family, the Clusiaceae or Guttiferae. Dr. Erwin Ting of the University of California at Riverside, has discovered that Clusia exhibits Crassulacean Acid Metabolism (CAM), a photosynthetic mechanism for conserving moisture previously known only in cacti and other succulents. The acronym is derived from the succulent plant family Crassulaceae, which includes stone crops (Dudleya and Sedum) and jade plant (Crassula). In the case of Clusia, CAM photosynthesis apparently aids in the establishment and growth of epiphytic seedlings until their aerial roots reach the soil and a permanent source of moisture and nutrients.

Crassulacean Acid Metabolism

CAM plants are able to store CO2 during the hours of darkness by combining it with PEP (phosphoenolpyruvate) to form 4-carbon organic acid molecules (malic acid). This chemical reaction is sometimes referred to as the "dark fixation of carbon." During the hot, daylight hours, when the stomata are closed to prevent the escape of vital moisture from plant cells, the 4-carbon acids break down releasing CO2 for the Calvin cycle (dark reactions), where CO2 is converted into glucose inside the stroma of chloroplasts. The adaptive advantage of this remarkable method of photosynthesis is that vital CO2 is available in the hot, daytime hours when the stomata are closed. Photosynthesis in ordinary plants (without this mechanism) shuts down because their CO2 level drops too low when their stomata are closed (when the stomata are closed, very little CO2 is able to diffuse into the leaf cells). CAM photosynthesis has been discovered in at least 20 plant families, including the cacti (Cactaceae), stonecrops (Crassulaceae), orchids (Orchidaceae) and bromeliads (Bromeliaceae). The appearance of this photosynthetic mechanism in the Clusia Family (Gutifferae) is yet another example of convergent evolution, where the same or similar characteristic (biochemical pathway) has developed in distantly related families. For epiphytic plants that develop on the limbs of other trees, such as certain orchids, bromeliads and Clusia, the benefits of CAM photosynthesis are obvious.

Pitch apple (Clusia rosea), another strangler on the Island of St. John, U.S. Virgin Islands. Unlike the strangler figs (Ficus), Clusia belongs to an entirely different tropical plant family, the Guttiferae. It has attractive pinkish-white blossoms followed by sticky, seed-bearing fruits.

The dried, dehiscent fruit of pitch apple (Clusia rosea), a tropical tree that grows epiphytically on other trees. Unlike the strangler figs (Ficus), Clusia belongs to an entirely different plant family, the Guttiferae. It has attractive, pinkish-white blossoms followed by sticky, ball-shaped, seed-bearing fruits. Clusia rosea was introduced into the Hawaiian Islands, and on the wet, northern coast of Kauai it lives up to its "boa constrictor" habit by strangling other trees.

Many tropical figs develop slender aerial roots hanging from the branches; however, in true banyan-type strangler figs enlarged aerial roots extend from the branches to the ground, giving the tree the unusual appearance of being supported by pillars. By this manner of growth the tree is able to spread outward almost indefinitely, and many Indian banyans (Ficus benghalensis) are of immense size and very old. One of the largest trees on record grew at the Calcutta Botanic Garden. It is listed in the Guinness Book of World Records (1985) as the world's largest (spreading) tree crown, with 1,000 prop roots and covering an area of four acres. The canopy of some banyans provides shade for entire villages. Alexander the Great reportedly camped with an army of 7,000 soldiers under a banyan. The Hindus regard the banyan as sacred, for it is said that Buddha once meditated beneath one. Probably the most revered tree in the world is F. religiosa, the sacred bo tree of Burma, Ceylon and India. It is said that Buddha sat under its shade for six years while he developed his philosophy of the meaning of existence. The striking heart-shaped leaves of the bo tree tremble in the slightest breeze like a cottonwood--a legendary tribute to the divine meditations of Buddha. The English name "banyan" comes from the "banians," or Hindu merchants who set up markets in the shade of these enormous trees.

A large Indian banyan (Ficus bengalensis) at the Gauguin Botanical Garden in Tahiti, French Polynesia. The trunks in foreground are large aerial prop roots from the enormous tree in the distance.

Banyans are not limited to India. On the scenic South Pacific islands of Tahiti and Moorea the Polynesian banyan (Ficus prolixa) clings to vertical volcanic cliffs, sending hundreds of aerial roots to the ground far below. Polynesian banyans also grow near native settlements and are considered sacred. In addition to providing shade, they have several interesting uses. Slender aerial roots are picked and used to treat skin cancer and other afflictions. The medicinal properties may relate to the milky sap containing ficin, a strong proteolytic (protein digesting) enzyme than can apparently also rid the body of parasitic worms. [The milky latex from several Central American strangler figs has also been used as a vermifuge.] The inner bark was also pounded into tapa cloth, a source of clothing for native Polynesians.

An unusual use for banyan-type figs of the Sikkim-Himalaya region employs "living bridges" across streams and gorges. Aerial roots from fig trees on opposite banks are tied together and then fuse and thicken. Another remarkable story comes from the Transvaal region of Africa. One traveler tells of a Bakone village with 17 conical huts built above the reach of lions on the limbs of one gigantic fig tree. See the following YouTube video:

On Lord Howe Island (east of New Guinea) grows another large banyan, Ficus macrophylla var. columnaris. According to I.J. Condit (Ficus: The Exotic Species, 1969), single large tree may cover more than one acre. In 1874, Ferdinand von Mueller, director of the Melbourne Botanic Garden, described this species as "One of the most magnificent productions in the whole empire of plants...The pendulous air roots, when they touch the ground, gradually swell into columns of the same dimensions as the older ones which have already become converted into stems, so that it is not apparent which was the original trunk; ...and thus it is impossible to say whence the tree comes or whither it goes."

Pillar-like aerial roots support a massive spreading limb of a Lord Howe Island Banyan (Ficus macrophylla ssp. columnaris) at the San Diego Zoo. In its native habitat, a single tree of this species can cover one acre of land.

In spite of their sinister common name, strangler figs are one of the most important components of tropical forest ecosystems. During the day hundreds of animals feed on the sweet fruits, including many species of pigeons, parrots, hornbills, toucans and monkeys. As night falls, the day foraging shift retires and flocks of fruit-eating bats descend upon the branches. Fig trees typically produce three or more crops of fruit a year, providing food throughout the year when other sources are in short supply. The fleshy, juicy fruits are full of small seeds which readily pass through the digestive tract of animals. In fact, the purgative effect of fig fruits on the bowels encourages its seeds to be widely dispersed--good strategy for an epiphytic opportunist. In addition to the prodigious fruit source, hundreds of animal species make their homes in the hollow trunk where the strangler fig has enveloped the decayed host tree. The cavities provide housing for myriad creatures, including geckos, frogs, anolis lizards, bees, wasps, beetles and ants. These trunk-dwellers in turn provide an additional food source for higher levels of the fig food web.

A massive strangler fig (Ficus cotinifolia) in Yucatan with numerous vinelike, aerial roots growing from the limbs. Some of the roots have fused (anastomosed) into large pillars. The decayed trunk of the host tree is still visible inside the strangler's web of fused aerial roots.

Although several species of wild figs are native to southern Florida and Baja California, fossil evidence indicates that strangler figs once grew wild in California about 40 million years ago, in a tropical forest much like present-day Yucatan. Today they are represented by several spectacular Asian and Australian trees originally planted by farsighted gardeners with a vision, almost a century ago. With a warming climatic trend during the next 10,000 years, accompanied by an increase in humidity and rainfall, the progeny of some of these exotic species quite possibly could assume their inherent epiphytic growth habit in southern California. Alien strangler figs in California might prove to be a horticulturist's nightmare, as they are today in some areas of southern Florida.

This large Moreton Bay fig (Ficus macrophylla) was planted in Glendora, California in the late 1800s. The enormous surface roots cover 1200 square feet (40 square meters). In its native habitat of eastern Australia, this species becomes a gigantic strangler.

Ficus villosa is a climbing vine fig native to the tropical rain forest of Borneo. Because of its aggressive, epiphytic growth habit in tropical regions it has made the Global Compendium of Weeds (GCW).

References About Strangler Figs & Banyans

  1. Armstrong, W.P. 1988. "Stranglers and Banyans." Zoonooz 61 (2): 16-19.

  2. Armstrong, W.P. 1990. "Stranglers in Paradise." Terra 29 (1): 32-40.

  3. Armstrong, W.P. and S. Disparti. 1988. "Wild Figs and Wasps of the Californias." Environment Southwest No. 521: 7-11.

  4. Condit, I.J. 1969. Ficus: The Exotic Species. University of California Division of Agricultural Sciences, Berkeley, California.

  5. Janzen, D.H. (Editor). 1983. Costa Rican Natural History. The University of Chicago Press, Chicago.

  6. Mitchell, A.W. 1986. The Enchanted Canopy. Macmillan Publishing Co., New York.

  7. Standley, P.C. 1917. "The Mexican and Central American Species of Ficus". U.S. National Herbarium Contributions 20: 1-35.

  8. Standley, P.C. 1930. "Flora of Yucatan." Field Museum of Natural History Botany Series, Vol. 3 (Publ. # 279). (Ficus, pages 159-161.)

  9. Standley, P.C. and J. A. Steyermark. 1946. "Flora of Guatemala." Fieldiana Vol. 24 (Part V). Chicago Natural History Museum. (Ficus, pages 30-48.)

  10. Ting, I.P., E.M. Lord, L. da S.L. Sternberg, and M.J. DeNiro. 1985. "Crassulacean Acid Metabolism in the Strangler Clusia rosea Jacq." Science 229: 969-971.

  11. Ting, I.P., J. Hann, N.M. Holbrook, F.E. Putz, L. da S.L. Sternberg, D. Price, and G. Goldstein. 1987. "Photosynthesis in Hemiepiphytic Species of Clusia and Ficus." Oecologia 74: 339-346.

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