Letters to the Editors

Spanish moss won't hurt your live oak tree

Editor's Note: The following letters are in rebuttal to a guest column by Gil and Ray Stanage regarding Spanish moss that was published on Feb. 14.

© St. Petersburg Times, published March 1, 2000

Dear Editor:

I must say I was a bit taken aback by an article I read recently in the Citrus Times headlined Spanish moss can grow to smother tree's foliage. As a biologist and professional naturalist, I cannot just sit by and let the information in this article go unchallenged.

I agree with the authors that there are about 23,000 different types of mosses in this world, but Spanish moss is definitely not one of them. Mosses lack true stems and roots and have no vascularization in their leaves. Spanish moss (Tillandsia useonoides) is neither Spanish nor a moss, but rather a true flowering plant native to the Southeastern United States. This lightweight, rootless plant is gray-green in color and hangs from tree branches like the long, tangled whiskers of an old man's beard.

The authors are correct when they state Spanish moss is not a parasite. It is actually a harmless commensal known as an epiphyte, or air plant, and gets its nutrients and moisture from the air, not from the tissues of the host tree. The tree is nothing more than a convenient structure on which to live. Spanish moss usually grows to a length of 3 to 6 feet, but often grows as long as 8 feet or even longer, and sways easily in the breeze, adding much beauty and grace to many trees in our area. In fact, Spanish moss is so common among our majestic live oaks that such a tree without its obligatory "moss" appears seriously lacking.

It can also be found growing on many other local trees, such as laurel oaks, pignut hickories, bald cypresses, flowering dogwoods, etc., but most people associate it primarily with the live oaks.

Contrary to the claim in the above mentioned article, it does not under normal conditions smother the foliage of the trees with which it has coexisted for many thousands of years. Look at any live oak with Spanish moss within its branches, and you will see the "moss" is simply draped thinly over the branches, while the tree's stems safely protrude through it with their terminal leaves very definitely outside any smothering effects. I will concede that Spanish moss could perhaps smother foliage if it falls off its host tree as a piled-up clump onto an unsuspecting azalea or camellia bush directly underneath.

There is a closely related air plant commonly called "ball moss" (Tillandsia recurvata), which appears quite different from Spanish moss in that it has long, thin, stiff leaves extending out only 6 to 12 inches from the plant's center. It actually looks like a tiny pineapple plant growing within the branches of a tree, which is not surprising because it is indeed related to the pineapple plant. In addition, there are three other local air plants (all within the genus Tillandsia) which have similar lifestyles to that of the ball moss.

But, despite what the authors claimed in their article, ball moss is definitely NOT a parasite. They state that it grows its roots into the tissues of the host tree to obtain moisture, and this weakens the tree so that the "moss" grows faster since the tree has little resistance. The reason the ball moss appears to grow faster on a weakened tree is there is more light available as the tree loses its foliage through some disease. The disease, however, could not have been caused by the harmless ball moss. One can observe ball moss living quite successfully on power lines stretching high over roads, which demonstrates they get all their sustenance from the air.

By the way, I must also mention that chiggers are arachnids (eight-legged creatures related to ticks and spiders), not insects, as stated in the article, and they do not normally live in Spanish moss but rather in grasses and low shrubs. Living near the ground allows them to more easily latch onto their victims.

So please don't be disturbed by the misinformation in that article and decide you must do something about the graceful, luxuriant growth of Spanish moss for the welfare of your trees. Your trees are just fine. Spanish moss is part of what makes Citrus County so beautiful.
-- Tom Ritchie, Floral City

Live oak trees survive after thousands of years

Editor:

The question of "Spanish moss" damage to trees just keeps coming up over and over for some reason. I suppose it's wonderful that some people don't have more to worry about than something that has been growing on and "smothering" oak trees for hundreds, probably thousands, of years, not to mention several hundred years on individual trees. How have these survived in the Southeast United States? Maybe this false belief is kept alive by an old publication by Tony Jensen of the Department of Forest Resources and Conservation.

He stated weak limbs laden with moss may break off and small branches may sometimes be smothered. I have tried to find this author to discover what evidence he had to support his statement about smothering, but he is no longer employed by the University of Florida or the state of Florida, nor is he a member of the Florida State Horticultural Society or the American Society of Horticultural Sciences. I doubt that the Stanages, in their article of Feb. 14, were referring to this publication anyway because it also discredits their claim about chiggers or redbugs.

Trees do get nutrients from the air: carbon, oxygen, hydrogen and minor amounts of other nutrients from rainwater. The issue of "smothering," however, would be with the exchange of gases, carbon dioxide and oxygen through the stomates that enables the chloroplasts to produce starches from nutrients transported primarily from the roots. Research has demonstrated that this process is operating at about 10 percent of its potential as things such as sooty mold (a fungus that grows on the sugar exuded from scales, aphids and whiteflies) shade leaves, sometimes tremendously, although the performance of the chloroplasts is not affected, no matter how thick we artificially grow this fungus. This is why antitranspirants haven't been shown to work. We just aren't able to close off enough stomates to affect the process.

The mineral composition of Spanish moss, which by the way is not a moss at all, is found to be similar to the air and not the oak tissue on which it is supported. The same thing can be said of the ball mosses. Both of these plants grow very well on board fences, power lines and many other non-living substrates. When I was growing up, some years ago, and power lines were covered with a clothlike insulation, these "mosses" were a major problem for the power company. My shade house has a chicken wire roof on which I grow Spanish moss for shade.

Ball moss grows well on brick walls and home siding. We could go on and on. I am sure that some limb breakage might occur if a heavily laden branch is weighted with water in a windy rain, but look around. How often do you see this under a tree?

The science is not there to show damage from Spanish or ball moss. If you are one of those who aren't interested in science, then you might wonder how the live oak has survived for so many thousand years with its branches covered with Spanish moss generation after generation. You might, if you are seeking some factual information, refer to a response written by Tom Ritchie of Floral City to the article by Gil and Ray Stanage on Feb. 14 or a new University of Florida publication by Dr. Nancy Arny on Spanish moss and ball moss available from your Cooperative Extension Office. Both Spanish and ball moss can be controlled with copper sprays, but before you rush out and start spraying you may want to read about the ecological relationships brought to bear in Dr. Arny's publication.

For chemical control, as of 1996, the following materials are licensed for control of Spanish moss and/or ball moss: TC Tribasic Copper Sulfate, Blue Shield, Basic Copper 53, Micro Flo Basic Copper 53, Micro Flo Copper 3 FL. It should be noted that there is evidence that copper-based herbicides and fungicide may cause damage to tender growth on oak trees.

As with all herbicides, when using these materials, read and follow label directions carefully. Please be advised also that many formulators of these products do not include Spanish or ball moss on their labels.

Be sure to check before you purchase, because if they aren't on the label, it is an illegal use of the product. Be advised also that copper will stain houses, driveways, sidewalks, etc. brown. This applies not only to yours but your neighbors' as well.

Andrew J. Rose Jr., multicounty agriculture agent, University of Florida Cooperative Extension Service

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