|Redwood tree (Sequoideae)|
The redwood trees are a subfamily (Sequoioideae) within the family Cupressaceae, the cypress trees. There are three living species within the subfamily: Sequoiadendron giganteum, Sequoia sempervirens and Metasequoia glyptostroboides. There were once many more species of redwood trees, but most have become extinct.
These trees are pyrophytes, which means they have adapted to protect themselves from fire. Because fire is common in the regions where they grow, redwood trees have developed thick, fire-resistant bark. Their cones open only after a fire. Due to better fire control in modern times, these trees are endangered.
Redwood trees can grow to be very large. The largest species, Sequoiadendron giganteum, can reach up to 94.8 m tall and 17 m across. The tallest tree in the world is a Sequoia sempervirens named Hyperion. The largest tree in the world by volume is a Sequoiadendron giganteum named the General Sherman Tree, after William Tecumseh Sherman.