First most the mass of a tree is not living consisting of dead cells. Secondly many plants reproduce vegetatively so that a grove of aspens or a field of goldenrods may actually be a single organism connected by underground roots. The Mendocino Tree in the Montgomery Woods State Preserve of California is 336 feet tall. Not everyone agrees that the Redwood is the tallest tree. Some claim that there have historically been taller specimens of Douglas Fir and a few claims for eucalypts in Australia have been made.
Redwoods can also be very old.
Trees with estimated ages of over 2200 years are known. Redwoods form magnificent forests along the Pacific Coast of northern and central California. This tree is over 36 feet in diameter and 113 feet around. The tree is called the Tule Cypress and is located in Santa Maria del Tule in Oaxaca, Mexico. Although you usually think of Bald Cypress as a denizen of the swamps of the southeastern United States, it grows well in drier areas as well and is commonly planted as an ornamental.