From Seed to Seed:
Plant Science for K-8 Educators

Epiphytes. One interesting group of plants is called the epiphytes. Relatively rare in temperate regions, epiphytes are quite common in tropical rainforests. An epiphyte is a plant that grows on another plant, neither harming nor helping it. For example, mosses can be epiphytic, growing harmlessly on tree trunks. More exclusively epiphytic plants are the bromeliads and some orchids.

Bromeliads are plants that commonly grow high in the branches of tropical rainforest trees. If you choose to build a rainforest in the classroom, as we suggest in Activity 17: Take a Hike, you could incorporate bromeliads into your design. They are often found in the joint where a branch meets the trunk; there, fallen plant debris collects, providing a source of nutrients to the bromeliad. Some species of bromeliad have cup-shaped leaf rosettes. The cup fills with water during the frequent rains, and the plant is able to use this supply to fill its water needs. Have students brainstorm how they will meet these needs in the classroom-in the absence of frequent rainfall. Although bromeliads "perch" in the branches, they do no harm to the tree. They photosynthesize their own food and their roots never penetrate the tree's bark, so they do not draw any of their nutrients from the host tree. They simply perch there, high in the canopy, where light is more plentiful than on the forest floor.

Epiphytic orchids can also be found perched in trees in the rainforest. Like bromeliads, they collect nutrients from organic debris. Orchids are able to fill at least some of their water requirements by absorbing water vapor through their long, aerial roots.

Now let's look at some less benign relationships between plants.