Its largest branch is almost seven feet in diameter. Barring accidents, it seems to be immortal. Muir was partially right. Chemicals in the wood and bark provide resistance to insects and fungi. The main cause of death for sequoias is toppling.
Sequoias have a shallow root system with no tap root.
Soil moisture, root damage, and strong winds can also lead to toppling. These behemoth trees sprout only from seeds so small and light they look like oat flakes. Mature trees may produce each year 2,000 chicken's egg-sized cones, collectively bearing 500,000 seeds dispersed only as cones are opened. Cones hang on the tree green and closed for up to 20 years. Douglas squirrels or the larvae of a tiny cone-boring beetle may cause cones to open, but fire is the key agent in the dispersal of seeds.