Undergrowth is the dense tangle of bushes, ferns, vines, and small plants that grow beneath the tall trees in a forest. While the tree canopy towers overhead, the undergrowth fills the space below, creating a thick layer of vegetation that can be difficult to walk through.

If you've ever tried to explore off the trail in a forest, you've probably encountered undergrowth: brambles that catch on your clothes, low branches that block your path, and leafy plants that hide the ground beneath your feet. In tropical rainforests, the undergrowth can be so thick it's almost impossible to pass through without a machete. In other forests, especially where tall trees block most sunlight, the undergrowth might be sparse and easier to navigate.

The undergrowth provides crucial habitat for countless animals. Rabbits hide in it, insects crawl through it, and birds nest in its branches. Seeds germinate there, waiting for their chance to grow toward the light. When a large tree falls and sunlight suddenly reaches the forest floor, the undergrowth bursts with new growth, racing to fill the gap in the canopy above.