The Mammoth Tree of California. This tree grows up to 350 or 400 ft. high, with trunk 20-40 ft. in diameter in a wild state, and is said to attain an age of 2000 to 3000 years. It rarely grows taller than 50 ft. in the British Islands. S. sempervirens (Taxodium), the Californian Redwood, grows as well but not quite so tall in good soil.