Q: I’m fairly new to the South and I have a question that none of the natives have been able to answer for me. I’m hoping you can. What causes Spanish moss to grow on one tree when the tree next to it has none? I know it sounds silly but this question is making me crazy!
A: Spanish moss (Tillandsia usneoides) is one of the signature plants of the Deep South. It is an epiphyte, meaning that it uses trees for support, but doesn’t draw moisture or nutrients from them, although rainwater running down the bark may supply it with both. You generally see it most often along the coast, because it needs high humidity and mild winter temperatures to survive.
Why do you see it certain trees and not others? It tends to favor:
• Trees that have lots of large, well-spaced branches
• Trees whose branches are more horizontal than vertical
• Trees with rough bark that provide a good foothold
Among its favorite hosts — live oak, bald cypress, red cedar, hackberry.
One additional factor is the willingness of the tree to be a happy host. Spanish moss can grow so profusely in a tree that it interferes with photosynthesis by blocking sunlight from reaching the leaves. So certain trees, such as camphor, release chemical substances that kill Spanish moss.
Hope this helps,