Ever notice that in addition to the leaves growing in the canopy of cypress trees, that there are also green leaves growing at the base of the trunks as well?
This is an excellent example of "commensalism," the long-term biological relationship between two organisms where one organism benefits while those of the other species neither benefits nor is harmed. In the case of the bald cypress trees found across the swamps of South Louisiana, the ferns, lichen, vines, and small shrubs grow on the cypress trees without harming them.
So how do these plants grow on the cypress trees to begin with? It's an ideal scenario, whereas the trunk characteristics of the bald cypress tree are designed perfectly for plant commensalism to take place. Due to the buttressing of the trunk and its many deep crevices, over time falling leaves settle on the trunk, decompose, and turn into a makeshift soil. Because this "soil" is typically very thin, only plants with shallow roots can survive. Wind and animals (primarily nesting birds) carry seeds or spores across the swamp, dropping them throughout and then the germination can begin. Rain and waves water these small plants helping them sustain life.
It's little micro-ecosystems just like the base of the bald cypress tree coupled with the sheer vastness of the Atchafalaya Basin, that makes any swamp tour at McGee's so special!