That depends on the type of tree. An old growth redwood forest, for example, will often have large areas with no trees except redwoods. The bottom ten feet of

That depends on the type of tree. An old growth redwood forest, for example, will often have large areas with no trees except redwoods. The bottom ten feet of the forest, where you walk around, can be nothing except smooth vertical trunks, with a thick covering of needles on the ground. No undergrowth at all, because the bottom of the forest lives in permanent shade, and the redwoods change the chemical balance of the soil in a way that makes it hard for other plants to grow.