What is an Epiphyll?
An epiphyll is a tiny organism — usually a moss, liverwort, or lichen — that grows directly on the surface of a living leaf. These miniature gardens on leaves are a signature feature of Costa Rica's cloud forests and wet lowland rainforests.
How They Establish
- Spores or fragments land on a leaf surface.
- High humidity and low light in the forest understory allow colonization.
- Epiphylls grow slowly, forming thin crusts, patches, or tiny cushions.
- They absorb moisture and nutrients from rain, mist, and leaf leachates.
Common Types
- Liverworts: Flat, ribbon-like growths — the most common epiphylls.
- Lichens: Crust-like patches of green, grey, or orange.
- Algae: Thin green films, especially on large, long-lived leaves.
- Mosses: Small cushions, less common as epiphylls than as epiphytes.
Effects on the Host Tree
- Light reduction: Heavy epiphyll cover can block 10–20% of photosynthetically active light.
- Drip-tip adaptation: Many tropical leaves have elongated tips that channel water and reduce epiphyll establishment.
- Leaf lifespan: Trees may drop heavily colonized leaves sooner.
Costa Rican Context
Cloud Forests
Monteverde and other montane forests are epicenters of epiphyll diversity — nearly every understory leaf hosts communities.
Lowland Rainforest
Epiphylls are abundant but less diverse, favoring the largest, longest-lived leaves in deep shade.
Why It Matters
- Biodiversity: Epiphyll communities are a hidden layer of forest diversity.
- Indicator: Abundance indicates high humidity and intact forest conditions.
- Leaf evolution: The drip-tip leaf shape common in tropical trees likely evolved partly to shed epiphylls.