Why Does Spanish Moss Grow on Trees?

Spanish moss (Tillandsia usneoides) is a common sight hanging from trees in many Southern states. Its silvery-grey foliage with slender leaves is picturesque, and rather gothic. In fact Spanish moss is not really a moss, but is related to bromeliads -- another type of plant that uses trees as a place to flourish.

Spanish moss grows only in areas of high humidity and high temperatures. In the U.S. it's found from Virginia through states to the South, and as far west as eastern Texas. It also flourishes in Central and northern parts of South America.

Spanish moss belongs to a class of plants called epiphytes. These are plants that live on minerals and other nutrients obtained from rainfall and from the air around them. They're sometimes referred to as "air plants." The plant's leaves have tiny, cup-like scales that trap water and extract the nutrients.

Spanish moss is most commonly associated with hardwood trees such as the live oak and the cypress, but it also has been seen growing on pines, pecans and other trees. Studies suggest that trees like the oak and cypress may have a higher availability of minerals necessary to the survival of Spanish moss, as more rainfall is collected on their leaves.

Spanish moss is not actually parasitic to the trees it hangs from. It takes some nutrients from decayed matter on the tree trunk, but it is not permanently rooted in the tree, and merely uses it for support. However, if a tree has a particularly heavy growth of Spanish moss, it can begin to suffer because of a lack of sunlight. Spanish moss also has a great ability to absorb rainwater, so after particularly heavy rains, it has been known that the weight of Spanish moss can break tree branches.

Although Spanish moss is occasionally seen hanging from telephone wires or other man made structures, this is usually stray moss that has been blown there by the wind. In fact the moss will generally only flourish and establish itself on trees, which provide a complete environment and a higher retention of rainwater in their leaves and branches. After the moss flowers, it produces seeds that become airborne and spread to nearby trees. They stick to the rough bark, and begin to sprout.