Institute of Food and Agricultural Sciences
Hendry County Horticulture News
Of all the trees on earth, the figs (Ficus spp.) certainly have the most bizarre growth forms and the most ingenious method of pollination. Many have numerous snakelike, aerial roots growing downward from the limbs and a peculiar aggressive growth habit that literally strangles other trees eventually forming a massive, buttressed trunk with huge surface roots spreading in all directions,. Although many 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" movie.
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, Eucalyptus, and Cassia. With the exception of the Hawaiian Islands, practically every tropical continent and island group has one or more indigenous species of fig. 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 - in one of nature's most amazing symbiotic relationships between a tree and an insect. The symbiotic wasps play a major role in the ability of different fig species to grow in a particular locality.
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 snakes, fuse together forming a massive woody envelope or "straight jacket" 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.
Here in south Florida, we have two native Florida strangler figs (Ficus aurea and F. citrifolia) which commonly attack palms, bald cypress, oaks and many other trees. 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.
In spite of their sinister common name, strangler figs are an important components of forest ecosystems. During the day many birds and animals feed on the sweet fruits. As night falls, the day shift retires and bats and other hungry creatures 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 encourages the seeds to be widely dispersed -- a good strategy for an epiphytic opportunist. In addition to the prodigious fruit source, a number 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 frogs, lizards, bees, wasps, beetles and ants. These trunk dwellers in turn provide an additional food source for higher levels of the fig food web.
Several unusual exotic species of Ficus, such as the commonly cultivated Benjamin fig (Ficus benjamina), Indian laurel fig (F. microcarpa), rustyleaf fig (F. rubiginosa), and Moreton Bay fig (F. macrophylla) have been planted in Florida and are among some of the most spectacular trees in parks and botanical gardens. Due to the introduction of wasp pollinators, some of these strangler figs produce viable seeds. They sometimes germinate in the crowns of palms and in crevices of buildings.
Another exotic fig, the banyan (Ficus bengalensis) produces enlarged aerial roots extend from the branches to the ground, giving the tree the unusual appearance of being supported by pillars. In this manner the tree is able to spread outward almost indefinitely, and many banyans obtain immense size and age. One of the largest listed in the Guinness Book of World Records covers an area of four acres.
Unfortunately, most of these introduced species have proved to be a nuisance due to their aggressive nature. In fact, some of the alien strangler figs have proven to be a horticulturist's nightmare. The massive, spreading roots of these enormous trees buckle pavement and concrete swimming pools, plug drainage and sewer lines, and can pose a serious threat to underground utilities.
Although the native strangler fig has its place in nature, most of the other introduced fig species are best avoided for residential landscape use and are at best curiosities whose use should be confined to parks and botanical gardens. Good luck and good gardening.
Gene McAvoy is the horticulture agent with the Hendry County Extension Service. Direct your horticulture questions to PO Box 68, LaBelle, FL 33975, e-mail - email@example.com or phone 863-674-4092 or 863-983-1598. You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle. Office hours are from 8:00 - 5:00.
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