Giant sequoias are the world's largest single trees by volume. Record trees have been measured to be 94.8 m (311 ft) in height and over 17 m (56 ft) in diameter. The oldest known giant sequoia based on ring count is 3,500 years old. Sequoia bark is fibrous, furrowed, and may be 90 cm (3.0 ft) thick at the base of the columnar trunk. It provides significant fire protection for the trees. The leaves are evergreen, awl-shaped,.12-24 inches long, and arranged spirally on the shoots. The seed cones are 1.5-3 inches long and mature in 18-20 months, though they typically remain green and closed for up to 20 years; each cone has 30-50 spirally arranged scales, with several seeds on each scale, giving an average of 230 seeds per cone. The seed is dark brown, (0.16-.20 in long and 0.039 in broad, with a 0.039 in wide, yellow-brown wing along each side. Some seeds are shed when the cone scales shrink during hot weather in late summer, but most are liberated when the cone dries from fire heat or is damaged by insects.

The giant sequoia regenerates by seed. Young trees start to bear cones at the age of 12 years. Trees up to about 20 years old may produce stump sprouts subsequent to injury, but unlike coast redwood, shoots do not form on the stumps of mature trees. Giant sequoias of all ages may sprout from their boles when branches are lost to fire or breakage.

At any given time, a large tree may be expected to have about 11,000 cones. Cone production is greatest in the upper portion of the canopy. A mature giant sequoia has been estimated to disperse 300,000-400,000 seeds per year. The winged seeds may be carried up to 590 ft from the parent tree.
Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Trunks of mature trees in groves are generally free of branches to a height of 66-164 ft, but solitary trees will retain low branches. It tends to grow at elevations from 4600-8400 feet.