Roots take in water and food from the soil for the tree. Most tree roots are in the top three feet of soil. A tree's roots often spread out much wider than its crown. Tree roots give fungi food the tree has made, and the fungi give back water and minerals. Mycorrhizae are partnerships between fungi and roots that help the tree take up water and nutrients.

The cambium cell layer is the growing part of the trunk. Sapwood is the tree's pipeline for water moving up to the leaves. As new rings of sapwood form, the inner cells of older sapwood turn into heartwood. Heartwood is the central, supporting pillar of the tree.

A trunk cut across shows a pattern of rings, and the number of rings shows how old a tree or limb is. The width of a tree's ring changes with the weather and other conditions of that year. Some living bristlecone pines are more than 4,000 years old. The General Sherman Tree is thought to be between 2,200 and 2,700 years old, as of November 2026.

Leaves make food for the tree. They get their green color from a pigment called chlorophyll. As nights get longer in autumn, trees get a signal that the growing season is ending, and the green chlorophyll fades. Yellow and orange colors in leaves come from carotenoids, which are in the leaf all summer. Most evergreen trees have needle-shaped leaves.

Evergreen trees stay green all year. A pine tree is an evergreen tree. Pine trees and other conifers carry their seeds in cones. Male cones are small and hold pollen. A maple seed has a wing. Squirrels hide acorns by burying them, and that moves oak seeds around.

Coast redwoods are the tallest trees in the world, as of November 2026. The tallest known coast redwood is about 380 feet tall, as of November 2026. Coast redwoods also take in water from fog, as of November 2026. Coast redwood bark is thick and protects the tree from fire. Bark keeps a tree warm in cold and cool in heat, and it keeps insects away.

Words to know

• fungi: root partners
• mycorrhizae: root-fungus partnerships
• cambium: growing layer
• sapwood: water pipeline
• heartwood: central pillar
• carotenoids: yellow-orange pigments