The Ecology of Spanish Moss (Tillandsia Usneoides): Its Growth and Distribution

The growth pattern of Spanish moss is one of alternately dominant dichotomous forking (scorpioid dichotomy). The non—dominant branch at each fork is a leaflike branch. The flowers, which are terminal on the pendant plants, are produced in South Georgia from the middle of April to the first of June. The subsequently formed capsule remains closed for 6 months and its remnants remain in the same position for a year. Spanish moss has a positive geotropic response when oriented in a horizontal position. The formation of several vertical plants on old horizontal stems is a means of vegetative reproduction. An almost direct relationship is evident between terminal growth and the percentage of solar radiation. Atmospheric moisture alone will not support growth; experimental plants die in 3—4 months with natural humidity but no rain. Rate of growth could not be correlated with moisture or temperature, but it was adversely affected by shade. Although Spanish moss does not appear to favor any one host, it is not often found on pines. Possible explanations for this scarcity are that pines are self—pruning, the dense leaves are a formidable barrier to wind—blown entry, and the proportion of intercepted rainfall is greater in pines than in broad—leaved species. The distribution of Spanish moss in the United States, limited to the Coastal Plain of the southeastern states, ranging from Texas to Virginia, may be related to major storm paths which arise to Mexico or cross other storm paths which arise there and move laterally over the Coastal Plain. Some of the plants may have been carried into Florida by storms from the islands in the Caribbean Sea. Spanish moss is able to survive and produce viable seeds outside the Coastal Plain, and ability of the species to survive in habitats completely dissimilar to those of the Coastal Plain areas is shown by its distribution in various physiographic regions of South America. The close relationship between Spanish moss and ponds in Georgia appears to be the result of unfavorable conditions elsewhere (such as fire and lumbering which remove suitable substrates), rather than conditions provided by the ponds.