A tree’s growth is caused by the specialized cells present at the ends of each tree’s shoots that form areas called meristems.
Trees grow from both the top and sides from growth points called meristems. Trees shoot new sprouts from the top and the tips of branches and continue upwards and outwards. As this happens the trunk and branches grow thicker to handle the weight.
Should the meristems be removed when a tree is cut, the tree would no longer be able to grow. This would trigger epicormic growth which is less stable as it is attached to the tree’s bark and not the heartwood..
Trees grow by the production of new cells in certain areas of the tree. These areas where cell division occurs are called meristems. A tree grows in height through meristems which are located at the branch tips.
Because the new growth happens at the tips of the branches, they can elongate into new branches making the tree wide from the top outwards.
Roots are also able to expand through the soil because of the meristems. What makes the tree grow in diameter is also because of a specific meristem called vascular cambium.
How does a tree grow in diameter?
The trunk of a tree is vital for limb support. It is also where moisture and the nutrients from root to leaf are transported.
Because of its important role in a tree’s life, the trunk has to lengthen and expand as the tree grows to help its search for moisture and sunlight.
A tree trunk grows in diameter through cell divisions in the cambium layer of the dark. The cambium contains the tissue cells that will help the trunk’s growth. They are found under the bark.
Cellular expansion
A new layer in the trunk is added continually every year through the formation of the xylem and phloem cells on both sides of the cambium. The layers you see in the trunk are called annual rings.
Xylem – Cells to the inside compose the xylem which allows for the transfer of nutrients and water. The fibers found in xylem cells supply the strength of the tree in the form of wood, while the vessels allow water and nutrients to flow to the leaves.
Phloem – Cells to the outside are what make up the phloem. These cells conduct sugars, amino acids, vitamins, hormones, and stored food.
The bark of the tree trunk is one of the most important parts of the tree that helps in keeping it alive and healthy. A damaged and unhealthy bark caused by insects or environmental damage will quicken the deterioration and death of a tree.
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5 stages of tree growth
A tree undergoes 5 stages to reach its full maturity. Here are the 5 stages of tree growth:
Seed
Seeds come in a variety of shapes, sizes, weights, and colors. They have evolved into different types for seed dispersal whether through wind, water, or animals.
A seed can sprout and grow anywhere as long as the conditions are favorable for germination and all the resources it needs to survive are available. Seeds can be dispersed on forest floors, open fields, yards, rocky slopes, and roadsides.
All seeds develop from male and female parts of the trees to produce fruits but they are not always easily recognized or edible. Some tree seeds have a protective shell such as acorn, pecan, or hickory.
Other tree seeds are also contained in fleshy fruits like black cherry, mulberry, avocado, lemon, or persimmon. There are also tree seeds that have a helicopter-like appearance when falling on the ground like certain maples and sycamores.
Sprout
If the environmental conditions are favorable to the seed, the embryo within the seed will germinate. It will grow, expand, and break through the seed coat.
The energy the embryo needs to grow depends on the supply of food stored in the seed. The root grows downward into the soil for the sprout to anchor and searches for water and nutrients.
The sprout, on the other hand, grows upward to seek the sunlight. Consequently, the leaves will develop which will then allow for photosynthesis to make its food.
Seedling
As the sprout starts to develop woody characteristics, the soft stem will begin to harden, change its color from green to gray or brown, and develop a thin bark for protective purposes.
More leaves will develop in newly formed barks that are searching for light. The roots of the tree will continue to grow and branch out and down. Most of the roots are near the surface of the soil to easily absorb water, nutrients, and oxygen.
The tree seedling must compete with other trees and plants for its share of water, nutrients, sunlight, and space. This stage of tree growth is the most susceptible to risks and death.
Seedlings are most vulnerable to threats like fire, flood, drought, insects, extreme weather conditions, animals, and diseases. If a seedling survives this stage, it is well on its way to the next phase.
Sapling
A tree is considered a sapling, the fourth stage when its diameter is between 1 and 4 inches at 4.5 feet. This is the standard height according to the Texas A&M Forest Service.
A sapling is the size of a small tree that is sold in a commercial nursery for transplanting to your yard. It is in its juvenile state where the tree is not mature enough to reproduce.
The length of the sapling stage depends on the species of the tree. It also experiences a similar type of competition and threats to that of a seedling. Trees that have longer lifespans stay in the sapling stage for a longer period, too.
Mature
If the sapling is continued to be favored by the environment with sufficient nutrients, sunlight, and water, it will continue to develop into a mature tree. In this stage, the tree will grow to show its species if its surroundings allow it.
It is also in this stage where flowers develop and reproduction persists. Fruits will start to form and seed dispersal can now also take place.
How long a tree stays in its mature stage depends on the species and its environmental conditions before it starts to decline. The oldest tree in the world is 4,853 years old which is a Great Basin bristlecone pine known as Methuselah.
Author: Ben McInerney is a qualified arborist with over 15 years of industry experience. He uses his in-depth knowledge of the tree service industry to give readers to most accurate information on tree service costs and helps to educate them about the benefits of using a certified arborist for tree trimming and removal work.
