Tree New Mexico (TNM) is a non-profit organization that has been planting trees in the Land of Enchantment for over 30 years in urban areas both large and small. Last year we were fortunate to participate in the Tree Steward program offered by TNM. The program lasted for 14 weeks during which we learned many surprising facts about trees and how they function.
The definition of a tree is a large woody perennial plant with a single main trunk that has the strength to stand on its own.
Just like people, trees are made up of cells, tissues and organs. Cells are the basic building blocks. In a tree they organize into structures like wood or bark. Tissues organize into leaves, stems, roots, flowers and fruit. The cells in a tree have walls made of cellulose (makes up the solid framework of a plant). Lignin (a substance that gives plants their sturdy structure and helps them conduct water) is deposited in the cell walls and helps to make the tree woody and rigid so the tree can stand on its own and support its weight as it grows larger.
As a tree grows the cells thicken with cellulose. Each layer forms inside the previous layer gradually blocking water and oxygen from the cell. The living part of the cell dies leaving a hollow structure. More than 95% of a mature tree’s trunk and branches are dead, hollow cells! This is important to know because if a tree is wounded by something mechanical like a string trimmer or a branch is broken by the wind, the tree cannot heal the wound. It can only seal off the wound with new cell growth.
The two main body structures of a tree are the root and shoot systems. The root system anchors the tree and collects water and nutrients. The shoot system develops stems, leaves, flowers and fruit. It also provides nutrition, respiration (through its leaves) and water. Both of these systems interact and a change in one can immediately affect the other. Practices like the topping of a tree result in a loss of the tree’s natural shape and beauty.
The root system of a tree is just as important as the shoot system. Since we can’t see the root system, it often gets little thought or attention. We were surprised to learn that the roots of a tree can extend 2 to 3 times the width of the tree’s canopy if there is available soil space. We also did not know that most of the roots of a tree are in the top 1 to 2 feet of soil.
Roots require oxygen, water and nutrients. Oxygen diffuses from the air into the top portion of the soil. Water comes from irrigation (watering) and any rain that falls. Nutrients come from the soil and water. About 90% of the water and nutrient absorption of a tree happens within a foot of the ground surface! For this reason, Tree New Mexico recommends trees have only natural mulch (wood chips, leaves) on the root area to aid the tree in absorbing water and nutrients. So you can see that using plastic and rocks on a tree’s root zone hinders the tree’s ability to absorb water and nutrients.
The Shoot System: Trees are different from shrubs because they have one main stem (the trunk) which divides into branches and smaller twigs. Twigs provide support structure for the leaves, flowers and fruit. Branches and twigs spread out to give the leaves as much sun exposure as possible to aid in photosynthesis. Photosynthesis is the food making process of plants where they turn light energy from the sun into chemical energy (carbohydrates). A tree chooses to do four things with the energy it produces from photosynthesis: grow, maintain, protect or reproduce. Depending on the season, the tree’s age, any stress it may be experiencing and other factors, the tree balances these functions.
These are just a few of the many exciting and fascinating things that we learned during our course with Tree New Mexico.
To learn more, visit Tree New Mexico’s website at treenm.org