Giant sequoia Sequoiadendron giganteum
This giant evergreen conifer, Sequoiadendron giganteum, is the largest (though not the tallest) tree in the world. With its distinctive spongy red bark and colossal stature, it is a native of California and the largest known specimen is known as General Sherman - 84 m in height, with the circumference of its trunk at ground level 31 m. It is estimated to be around 3,200 years old.
The giant sequoia has small seed cones, each measuring a mere 5-7 cm, which take at least two years to ripen and many cones remain green and unopened for anything up to 20 years. Fires are essential for reproduction to take place. The bark is fire resistant so the tree is left unharmed while the other plant life around it is cleared, a prerequisite for seedlings to grow, helped along by a layer of ash as a seedbed. The heat from the fire causes the cones to open, dispersing the seeds on the wind.
The speed at which Sequoiadendron giganteum grows can be nothing short of phenomenal. In Italy, a young tree reached a height of 22 m in just 17 years. Growth rates depend largely on the habitat and weather conditions and while it can survive in temperatures as low as -30°C, it tends to flourish in a humid environment that has dry summers and snowy winters.