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A very common question is the tree growth rate and how it varies from the different species? From the time of seed germination to the death of a tree, it never ceases to grow. 

Tree Growth Rate

A tree’s growth rate changes as it moves through different stages of development: seedling, sapling, maturity, and senescence. In nature, trees reproduce primarily by seed, though some species also spread clonally. A tree’s genetic makeup determines its potential maximum age, height, and width. However, environmental factors also play a major role. Soil type, drainage, water availability, fertility, light, and exposure all influence growth.

Because of these variables, tree growth rates are generally classified as slow (less than 12 inches per year), medium (13–24 inches per year), or fast (more than 25 inches per year).

World’s Tallest Trees

In this day and age, the Coast Redwood trees (Sequoia sempervirens) represent the world’s tallest single-stemmed plants. It is an evergreen coniferous monoecious softwood species, which begins coning at about 10-15 years of age; and grows at the extraordinarily fast rate of 5-7 feet per year as a younger tree. The Coast Redwood is a prolific seed producer, bearing many cones about 3 inches in length; containing small seeds no larger than those of a tomato. The record of the tallest tree is in California; reaching 379 feet tall.

This champion tree begs the question of how do trees grow so tall and what limits their maximum stature. Recurring to our initial question on the behavior of growth of a tree. 

It is important to highlight that the growth patterns of all dicot trees are similar, but they are different from other plants which are popularly called “trees,” such as palms (monocots).

Tree Growth and the Production of New Cells

Furthermore, continuing with the Coastal Redwood example, trees grow by producing new cells in four specific locations on the plant. Branch tips (buds) result in trees increasing their height. Root tips grow to build a huge lateral root system which drop anchor in the soil and rock; to support the massive tree as it grows taller.

Furthermore, the production of male and female cones is important for the new cell development on branches. As trees increase the diameter of their trunk and branches by producing new cells in the cambium layer (xylem and phloem); which is in between the outer layer of bark and the inner sapwood. Besides, the sapwood contains vascular bundles which transport water and nutrients within the tree.

Tree Growth and Development: Heartwood

The heartwood represents the core of the tree and is the densest wood. Contrary to some popular beliefs, tree trunks do not elongate as they grow, they only increase in diameter. Coast Redwoods reproduces by seed, but if a tree falls or is cut new sprouts will develop from the stump or down the tree root system. This tree produces high-value lumber.

One of the most intriguing questions for scientists is how and why is height limited in these tallest of plants; when trees never cease growth. Studies of the Coast Redwood evidence that leaves at the top of the tree are smaller than those lower down. This may be the result of a hydrostatic limitation. As at about 380 feet in height the tree cannot pump water and nutrients any higher and hence height ceases.

Like all trees, Coast Redwoods ultimately reach senescence; in their life span of 500-700 years or longer. Old trees lose vigor and are less able to recover from physical damage caused by lightning or wind; and diminish their resistance to pests and diseases. Nonetheless it is only in forests under protection where the trees die of old age; elsewhere chain saws end their life during maturity.

Multi-stemmed Trees

Beyond the Coast Redwood, two remarkable multi-stemmed trees also reproduce both by seed and by cloning. One example is the Banyan tree (Ficus benghalensis). It spreads by sending aerial roots down from its branches, which take root and form new trunks. Over time, a single tree can expand outward and cover an entire acre of land.

Another example is the Aspen (Populus tremuloides). Aspens reproduce through lateral roots just below the soil surface, which send up new stems. These connected trees form massive colonies of genetically identical individuals. Some of these colonies rank among the largest living organisms on Earth, stretching up to five miles. The largest known clone, located in Utah, is estimated to be around 80,000 years old.

Despite their impressive size and spread, neither of these trees grows especially tall.