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

If you answered 15 feet above the ground, I’m afraid that’s not correct. The horseshoe will always be 5 feet off the ground. Trees increase in height by adding growth at the top, not the bottom, so a branch 5 feet above the ground stays at that level.

The growth of woody plants is fascinating and each year trees and shrubs produce a visible record of their growth. In the fall, when woody plants go dormant, we can look at these signs to know if the plants are healthy or stressed, based on their growth signs.

Each growing season is different, with variations in humidity, temperature, insects and diseases. Certain years are optimal for growth and the growth signs of the woody plant reflect this. Some years are stressful, with growth hampered by drought or disease, and the clues left reflect slowing growth.

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

Trees and shrubs grow in two ways. They spread higher and wider as the trunks and branches elongate, with individual trunks and branches also increasing in diameter and becoming larger.

Each growing season, trees, for example, add another layer of wood to the trunk, called an annual ring, which increases the diameter of the trunk. When a tree is felled, we can count the annual rings on the surface of the stump to determine the age of the tree, with each ring representing a year.

You can tell if the growing season was favorable or stressful by comparing the size of the rings. For example, during very wet growing seasons, the annual rings are wide, indicating that the tree was happy.

Chris Flynn / The Forum

During drought years, the annual rings are very narrow, demonstrating that the tree was not growing much because the stress was affecting its health. These rings create a historical record of woody plant performance each year.

A tree’s annual growth can indicate its health. Obviously, we’re not going to cut down a tree to examine the width of this year’s annual ring. There are other ways to view annual growth.

In addition to examining annual trunk rings, we can check branch length, which can indicate whether a tree was happy or suffering. A healthy tree or shrub should produce growth typical of its type. For example, a healthy young cottonwood tree typically grows at least 25 inches each summer, often more, while 8 inches of growth is suitable for a healthy oak tree.

Chris Flynn / The Forum

To measure a branch’s growth this year, start at the outer end of the branch and follow inward to a point where you see a raised, circular ring-shaped projection called a “growth scar.” This scar shows where last year’s growth stopped and this year’s spring growth began.

By measuring from the growth scar outward to the tip of the branch, we can assess the growth of the woody plant this year. Fast-growing trees and shrubs can easily reach 25 inches or more in length each growing season.

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

If a woody plant is making decent progress in branch growth, this generally indicates that it is healthy and that the growing season provides adequate moisture with minimal insect or disease pressure.

Chris Flynn / The Forum

But if a woody plant produced only one or two inches of growth on each branch, as evidenced by growth scars, the tree or shrub was stressed. Drought, heat or insect feeding can all reduce growth.

How did our trees and shrubs perform this year? Trees that have succumbed to the disease, such as ornamental crabapples that lost all their leaves in midsummer, likely grew very little this year, perhaps only an inch or two, when the growth scars are located and measured.

Other plants, like our own young lilacs 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 branch growth that may or may not have happened this year, we can also look to the future. To assess the health of a woody plant, look for buds along the twigs and branches. Visible, fresh, moist buds promise a bountiful spring next year.