In the fall, these tips will help determine whether trees and shrubs are healthy – InForum

I have an old math problem for you. If you hang a horseshoe on a tree branch 5 feet above the ground and the tree grows 1 foot per year, how tall will the horseshoe be after 10 years?

If you answered 15 feet above the ground, I’m afraid that is incorrect. The horseshoe will still be 5 feet above the ground. Trees grow in height by growth at the top rather than at the bottom, so a branch 5 feet above the ground will remain at that level.

The growth of woody plants is fascinating, and each year the trees and shrubs provide visible evidence of how much they have grown. In the fall, when woody plants go dormant, we can study these signs to see if the plants are healthy or stressed based on their growth signs.

Each growing season is different, with different humidity, temperatures, insects and diseases. Some years are optimal for growth, and the woody plant’s growth symptoms reflect this. Some years are stressful: growth is stunted by drought or disease, and the clues left reflect slowing growth.

What are these visible signs of growth that show how our trees and shrubs have grown this year? Understanding how trees grow is key to knowing what to look for.

Trees and shrubs grow in two ways. They stretch taller and wider as the trunks and branches become longer, with individual trunks and branches also increasing in diameter and becoming thicker.

For example, during each growing season, trees add another layer of wood to the trunk, called a growth ring, which increases the diameter of the trunk. When a tree is cut down, we can count the annual rings on the surface of the stump to determine the age of the tree, with each ring corresponding to a year.

By comparing the size of the rings, you can determine whether the growing season was favorable or stressful. For example, during a growing season with abundant moisture, the annual rings are wide, indicating that the tree is happy.

In dry years, the growth rings are very narrow, indicating that the tree has not grown much because stress has affected its health. These rings create a historical record of how woody plants grow each year.

A tree’s annual growth can tell how healthy it is. Obviously, we are not going to cut down a tree to test the width of this year’s annual ring. There are other ways to estimate annual growth.

In addition to examining the growth rings of the trunk, we can check how long the branches have grown, which can indicate whether the tree was happy or suffering. A healthy tree or shrub should produce growth that is typical for its type. For example, a healthy young cottonwood tree typically grows at least 25 inches each summer, and often more, while 8 inches of growth is sufficient for a healthy oak tree.

To measure how much a branch has grown this year, start at the outer tip of the branch and work inward to the point where you see a raised, circular, ring-shaped projection called a “growth scar.” This scar marks where last year’s growth stopped and this year’s spring growth began.

By measuring the distance from the scar to the tip of the branch, we can estimate how much the woody plant has grown this year. Fast-growing trees and shrubs can easily grow 25 inches or more in length each growing season.

Medium-growing woody plants can add 12 to 24 inches per year, while slow-growing plants grow 8 to 12 inches per year.

If a woody plant is making decent progress in growing branches, this usually indicates that it is in good health and the growing season provides adequate moisture with minimal exposure to insects or disease.

But if a woody plant only produced an inch or two of growth on each branch, as evidenced by growth scars, the tree or bush was stressed. Drought, heat, or insect feeding can slow growth.

How have our trees and shrubs fared this year? Trees that have succumbed to disease, such as ornamental apple trees that have lost all their leaves by mid-summer, have probably grown very little this year, perhaps only an inch or two if growth scars are located and measured.

Other plants, such as our own young lilac on a well-drained slope, produced 18 inches of new growth, measured from the branch’s growth scar to the outer tip.

In addition to looking back at the industry growth that has or hasn’t happened this year, we can also look ahead to the future. To assess the health of a woody plant, look for buds on the twigs and branches. Visible, fresh, moist buds promise a bountiful spring next year.