A Basic Guide to How Trees Grow


There are a lot of misconceptions about how trees grow and tree development even though they are all around us. Taking the time to study how a real tree grows can reveal some surprising mechanisms that make up these complex plants. There are many intricate systems within a tree which allows it to be the sturdy, statuesque body that they are.


When you think of trees, you should look at them as a collection of annual plants. Each plant grows at the end of a large, interconnected plumbing system and we will call these plants twigs. Each twig will create leaves, flowers and fruit as part of a tree. When considered on their own, they are like any other plant, but what sets them apart is their connection to a larger system. The branching system of the tree will distribute water, sugar and hormones to and from the twigs while regulating the growth and evolution of the tree structure.

The Flow of Water

Older branches will only have a thin outer layer just under the bark which is living tissue. The rest of the branch is made up of dead cells. These cell walls will provide the structural strength that the tree needs to grow tall. The sponge-like structure of the cells will also suck up the water from the tree roots and pass it through to each branch and all the way to the leaves. The water in the tree will be used in a number of ways. As the water moves through the structure it will be filtered for minerals and nutrients. A steady flow is required to ensure that the tree has all the nutrients it needs and that the leaf's surface evaporates water into the heat of the sun. The evaporation of water will dry the sponge and allow it to suck up more water from the soil.

The Flow of Sugar

The leaves of the tree will also use water to perform photosynthesis which is part of the flow of sugar. Leaves will absorb energy from the sun and use this to bind water and carbon dioxide into a form of sugar. The tree will use these sugars as a form of energy. The flow of sugar will take place in the living tissue of the branches as the leaves fill it with energy and the connected cells will draw on the energy when needed. All aspects of the tree are connected cells from the roots to the buds and trunk.

The Flow of Hormones

The flow of water and sugar will help to distribute hormones throughout the tree. The hormone Auxin which regulates growth is produced by the apical meristems or the tips of the branches which produce new cells. This hormone is necessary because it informs the branches lower down to lay low and is distributed through the flow of hormones.


While the twigs of the tree will take orders from the hormones flowing through the tree system, they are still individualistic plants. The life of the twig starts with a bud, at the end of each branch and at the base of each leaf is a bud. This contains the embryonic start of a twig which is within a protective cocoon to help it survive winter.


Each year, there are a huge number of twigs which grow from the protected buds. Twigs are considered the eyes and ears of the tree. While trees cannot hear they do have other senses which they can use. The twigs will use these senses to determine where they should be growing. One of the senses a tree has is balance which it uses to grow against gravity. Biologists have named this gravitropism and it allows the tree to grow up while its roots grow down. Light is very important to trees as it is their food so it is unsurprising that they have a sense for it. Twigs will sense different hues of light and when they get too little they will start to grow in the hopes of finding some.

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