Chapter 1 Tree Anatomy
Trees are more than the sum of their parts. To fully appreciate proper care of a tree, it’s important to understand the basic structure and growth of a tree, not unlike how people in the healthcare professions must learn human anatomy and physiology before they can practice medicine. The eight basic parts of a tree are the leaves, branches, trunk, cambium, xylem, phloem, bark, and roots.
Parts of a Tree
The most aesthetically appealing part of a tree is the crown -- comprised of a tree’s branches and leaves. Besides its pleasing appearance, the crown is where food for the tree is formed via
photosynthesis. Photosynthesis is the process of using sunlight to turn carbon dioxide and water into sugar and oxygen. Without the process of photosynthesis, the earth’s atmosphere would be inhospitable to life as we know it. As we work our way down the tree, branches continuously merge at unions, eventually forming larger limbs. As limbs grow and converge, they gradually increase in diameter until they merge with the trunk. Professional arborists are trained to inspect these main unions where large limbs attach to the trunk, as this can be a common, and often preventable, point of failure in a mature tree. The trunk of the tree serves an obvious structural role, and its strength must be proportional to the size of a tree’s crown for a tree to withstand the forces of nature. It also functions as a highway for the transport of water, nutrients, sugars, and growth hormones.
The most visible parts of your trees will be some of the most important sections of the tree to protect.
Near ground level, a tree’s trunk transitions into the below-ground root system. This transition zone is referred to as a tree’s “root flare” or “root collar.” Force from a windstorm or other weather hazard is transferred through a tree and then distributed down to the root system through the root collar. This area can be a particularly vulnerable part of a tree since most wounds occur at ground level. Wounding or excessive moisture trapped against this part of a tree can invite decay pathogens to enter, which is why protective measures should always be taken during construction or re-grading (the addition or removal of soil) around a mature tree. Lastly, roots absorb and transport water, minerals, and stored energy in the form of starches. Roots also produce growth hormones that allow all parts of the tree to work in conjunction by sensing environmental risks such as drought and soil temperature. Roots anchor the tree and keep
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