Meanings of dense fern in English

All the way the dense fern foliage arched overhead, throwing down deep shadows.

A tiny stream flowed out of a dense fern-brake, slipped down a mossy-lipped stone, and ran across the path at their feet.

One moment they were sunk within a dense fern meadow and now they stood in grounds dominated by giant trees, the under-canopy relatively clear.

I heard the motors first, deep downriver, the sound burbling and groaning through the trees and slipping through the dense fern and slowly growing loud.