Big tree is a general term that can describe any large tree, but it also has specific meanings worth knowing.

In everyday use, a big tree is simply a tree that's notably large, whether tall, wide, or both. A centuries-old oak with a trunk so thick that five kids holding hands can barely circle it is a big tree. So is a towering redwood that stretches hundreds of feet into the sky.

The term “Big Tree” (capitalized) is sometimes used as a common name for the giant sequoia, one of the most massive living things on Earth. These trees grow in California's Sierra Nevada mountains and can reach over 250 feet tall, with trunks more than 30 feet across. The most famous giant sequoia, called General Sherman, weighs as much as ten blue whales.

Scientists and foresters also use “big tree” to identify record-holding specimens of each species. Every state keeps a registry of its biggest trees, measured by a formula combining height, trunk width, and crown spread. Finding and documenting these champion trees helps scientists understand how large each species can grow under ideal conditions. Some of these big trees are over a thousand years old, meaning they were already towering giants before medieval castles were built.