Trees hold some of the biggest records in nature. Coast redwoods are the tallest trees in the world, as of November 2026, and the tallest known coast redwood is about 380 feet tall, as of November 2026. Hyperion, the tallest living tree, is estimated to be between 600 and 800 years old, as of November 2026. For age, Prometheus, a bristlecone pine in Nevada, was found by counting its rings to have 4,862 growth rings, and it was estimated at being 4,900 years old, the oldest known tree of its time. Some living bristlecone pines are more than 4,000 years old.

A trunk cut across shows a pattern of rings, and the number of rings shows how old a tree or limb is. In places with cold winters, a tree's cambium rests in winter and grows in summer, and in spring, when a tree is growing fast, its xylem cells are large with thin walls. The width of a tree's ring changes with the weather and other conditions of that year, so drought makes narrow rings while plenty of rain makes wider rings. Scientists learn about past weather patterns and forest fires by studying the annual rings of trees, and the science of studying the past by looking at tree rings is called dendrochronology.

Unlike animals, plants have no heart-like pump to move fluid through their vascular system. Sapwood is the tree's pipeline for water moving up to the leaves, and xylem carries water and minerals up from the roots to the leaves, while phloem carries food made in the leaves to the branches, trunk and roots. Plants lose most of the water their roots take in to the air through their leaves, a process called transpiration, and in fact plants keep less than 5% of the water their roots absorb.

Roots take in water and food from the soil for the tree. Most tree roots are in the top three feet of soil, and a tree's roots often spread out much wider than its crown. Giant sequoia roots are shallow but spread wide. 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.

Redwood forests grow naturally in a narrow band along the Pacific Coast, from central California to southern Oregon. Mature coast redwoods are resistant to fire because of bark 12 inches thick and a lack of flammable pitch or resin. Fire is part of the life cycle of giant sequoias. The General Sherman Tree is the largest tree in the world by trunk volume, at 52,508 cubic feet, as of November 2026. It stands 275 feet tall and is more than 100 feet around, as of November 2026. Giant sequoias are known to reach ages of up to 3,400 years, as of November 2026, though they are not the world's oldest trees.

Leaves make food for the tree, and 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. Shortening day length is the most dependable seasonal signal for autumn leaf color, more than chilly mornings. Yellow and orange colors in leaves come from carotenoids, which are in the leaf all summer.

Evergreen trees stay green all year, and a pine tree is an evergreen tree. Most evergreen trees have needle-shaped leaves, and the narrow needles of a Douglas fir can expose as much as three acres of chlorophyll surface to the sun. Pine trees and other conifers carry their seeds in cones.

Here is what wood is used for. Heartwood is the central, supporting pillar of the tree, and a heartwood post only 12 inches long and 1 by 2 inches across can hold up twenty tons. The lumber in the General Sherman Tree would be enough to build 120 average-sized houses. In a paper mill, the cellulose fibers from wood are trapped on a wire screen as the water drains away, and they stick to each other to form the paper web. Wood composite technologies have been used for decades to create building and home furnishing products.

Words to know

• dendrochronology: tree-ring dating
• transpiration: leaf water loss
• mycorrhizae: root-fungus partnerships
• sapwood: water pipeline
• carotenoids: yellow-orange pigments
• cambium: growing layer