The weeping fig, or Ficus benjamina, is one of the most popular ornamental trees in the U.S. You've probably seen potted figs growing in hotel lobbies, restaurant dining areas and doctors' waiting rooms. It's popular outdoors as well. It's adaptable to a wide range of conditions, and it tolerates shaped topiary style pruning. But given the right circumstances, Ficus benjamina can become a menace.
Ficus benjamina, like many ficus species, may begin life as an epiphyte. This term refers to plants that grow on host trees in a non-parasitic relationship. Instead of stealing nutrients from their hosts, epiphytes gather nourishment from air, rain and composting materials available on tree branches. Fruit-eating birds and bats drop their seeds high in the branches of trees in their native rain forest. There, they germinate and grow long roots, which secure them to their hosts. The appearance of these long aerial roots dangling the length of the host tree gives Ficus benjamina its common name: "weeping fig."
Ficus trees that germinate epiphytically are often called "banyans." The word may also be used to refer to the aerial root structure.
Ficus species are often known as "strangler figs" for the effect they have on their host trees. Even though they are not parasites, they often manage to kill their hosts via shading, strangulation and root competition.
Strangulation occurs as the ficus roots wrap around the host tree's branches and trunk. As the roots grow thicker, they crush the bark of the tree and the phloem and cambium layers underneath.
Before the strangulation effect becomes fatal, the ficus may instead kill its host tree with too much shade. As the ficus grows larger, its overshadowing foliage robs its host of more and more sunlight. If this goes on, photosynthesis will cease, and the tree will die.
Meanwhile the ficus's roots are heading for the ground. Once they reach it, they grow vigorously in all directions, generally outpacing the roots of the host tree in growth. Most of the available moisture and soil nutrient content goes to the ficus, and the host tree starves.
Destroying Historic Structures
An epiphyte can germinate in the cracks of old masonry, causing further destruction as they grow to these walls. Precious historical buildings crumble under the onslaught of aerial ficus roots.
Destroying Foundations and Utilities
The roots of an epiphytic ficus, once they reach the ground, spread out rapidly as they develop a network of new tree trunks surrounding the original host tree. Their growth destroys concrete structures such as pavement, building foundations and in-ground swimming pools. They can easily plug drainage and sewer conduits. They also threaten destruction to buried utility pipes and conduits.
Ficus benjamina has the potential to become an invasive species and cause destruction in warm, humid regions of the United States. Several other ficus species have, menacing the local trees and historical buildings of Maui. But each ficus species needs a particular species of wasp to pollinate it, and the U.S. has largely avoided introduction of the wasp necessary to the proliferation of F. benjamina. Thus it remains safe to propagate the weeping fig by cuttings and grow it ornamentally both indoors and out.
For a ficus species which is exhibiting destructive behavior, possibilities for controlling its spread include careful application of herbicides and introduction of ants and mites which prey on the pollinator wasps.