Underbrush is the tangle of small plants, bushes, shrubs, and young trees that grow beneath the tall trees in a forest. When you walk through woods, the stuff that catches at your ankles, blocks your path, and makes you push branches aside: that's underbrush.

It's called underbrush because it grows under the forest canopy, in the shadows of bigger trees. This thick layer might include ferns, berry bushes, saplings, vines, and all sorts of leafy plants competing for whatever sunlight filters down through the branches above.

Underbrush serves an important purpose in forests. It provides shelter and food for countless animals: rabbits hide in it, birds nest in it, and deer browse on it. But underbrush also creates challenges. Hikers find it difficult to navigate through dense underbrush without a clear trail. Firefighters worry about underbrush because it acts like kindling, helping forest fires spread rapidly from the ground up into the tree canopy.

Forest managers sometimes deliberately clear underbrush through controlled burns or manual removal to reduce fire danger and help larger trees grow stronger. However, removing too much underbrush can harm the forest ecosystem by taking away animal habitats and disrupting the natural cycle of decomposition that enriches the soil.