Some plant species, called epiphytes , grow directly on the surface of the giant trees. These plants, which include a variety of orchids and ferns, make up much of the understory , the layer of the rainforest right below the canopy. Epiphytes are close enough to the top to receive adequate light, and the runoff from the canopy layer provides all the water and nutrients they need, which is important since they don't have access to the nutrients in the ground. This tree has become covered in epiphytes. Note the vines and thick root balls that have formed in the branches.
Some epiphytes eventually develop into stranglers .
They grow long, thick roots that extend down the tree trunk into the ground. As they continue to grow, the roots form a sort of web structure all around the tree. At the same time, the strangler plant's branches extend upward, spreading out into the canopy. Eventually, the strangler may block so much light from above, and absorb such a high percentage of nutrients from the ground below, that the host tree dies. When the host decomposes, the strangler's lattice of roots remains, giving the plant the structure it needs to reach from the forest floor to the canopy.