Saturday, May 28, 2011

Strangler fig

Strangler fig, originally uploaded by Elizabeth Smith.

A fascinating tree found in the tropical hammock areas of south Florida is the strangler fig. It is a member of the fig genus, which in turn belongs to the mulberry family (Moraceae). The common name comes from its frequent habit of germinating in the tops of trees, sending encircling roots down along the trunk of its “host,” which usually results in the death of the original tree.

Strangler fig is not a true parasite as many people think. It starts life when a bird eats the fruit and then eliminates the seeds, usually from a perch high above the ground. The seed lodges in a crevice of rough bark, the crotch of a tree, or in the base of the fronds of a palm tree. After germination, the seedling lives on nutrients and water from the air while it sends aerial roots to the forest floor; it does not take any sustenance from the host tree.

Once the roots can take up water and minerals from the soil below, it grows further, competing with the host tree for sunlight and nutrients. The roots enlarge and often encircle the host tree, preventing it from growing. The host tree often dies later, shaded out by the fig’s canopy of leaves, and weakened by the growth of its roots. Strangler figs will also germinate in the soil, developing a conventional trunk, and can grow to 50 feet high.

The shade of its broad crown is welcome on our hot Florida summer days, its canopy composed of distinctive deep green leaves with a pale midrib. The color of the fruit inspired the scientific name of Ficus aurea (Golden Fig). The yellow to sometimes reddish-purple fruit is valuable to birds and other wildlife, and are reportedly edible for humans as well. The milky sap contains latex, which was used historically as a chewing gum – but is also a skin irritant for many people. The elliptical to oblong leaves are the larval food of the ruddy daggerwing butterfly.

The pointed tip on the end of the leaves is sometimes referred to as a “drip tip,” a tropical leaf design that allows for quick water drainage. It channels rainfall to the end of the leaf where it drips off. It’s thought that it helps protect the canopy from getting too top heavy with water, and protects the leaves from fungus. Another theory is that the dripping (instead of sheeting) action also protects the roots from too much soil erosion.

The fruits of the fig family are unusual: the inflorescence is turned inwards inside of the “berry.” In other words, the inside of the fruit contains tiny flowers that grow on the inside, toward the center. This presents a problem for normal pollinators, but a tiny wasp has developed a relationship with the fig family. You can read more about this relationship here.

The different forms that the roots of the strangler fig take are amazing and often quite artistic. The pale gray smoothness of the trunks reminds me of intertwining elephant trunks, and it amazes me the ways the aerial roots grow together and meld, sometimes creating intricate patterns.

To learn more about the strangler fig:

You can view these on my Flickr photostream, just click the caption on the top image.