Overstory #69 - Some Tree Basics

Editor's Note

This is the second in a three part series by special guest author Dr. Alex L. Shigo, retired chief scientist of the U.S. Forest Service and author of numerous books including Modern Arboriculture. Understanding trees and how to plant them, and planting the right tree in the right place are essential for tree planting success. Here Dr. Shigo introduces some key "tree basics."

Some Tree Basics

Trees are plants that are:

• perennial--live for several to many years
• woody--have tough cell walls of wood
• shedding--use and shed woody and non-woody parts
• compartmented--made up of many compartments.

Trees usually have a single stem over three yards (meters) tall.
Shrubs usually have many stems less than three yards (meters) tall.

Some champion trees:

• Giant sequoia (Sequoiandendron giganteum): Some over 2000 tons
• Swamp ash (Eucalyptus regnans): Some almost 300 feet (90 meters) tall
• Monkeypod (Albizia saman): Some trees with crown diameters of almost 200 feet (60 meters)
• Banyan (Ficus benghalensis): It takes 10 minutes to walk around the perimeter of the crown of a giant banyan tree in Calcutta
• Bristlecone pine (Pinus longaeva): Some are thought to be over 5000 years old

A brief overview of some unique features of trees

Trees are the tallest, most massive, longest-lived organisms ever to grow on earth.

Trees, like other plants, cannot move. However, trees, unlike other plants, are big, woody, and perennial, which means they are easy targets for constant wounding.

Trees are super survivors mainly because they grow in ways that give them defense systems that are highly effective against infections from wounds.

Trees have the capacity to adjust rapidly to changes that threaten their survival.

Animals move to get food, water, and shelter. They move to avoid destructive agents. When animals are injured and infected, processes of restoration and repair start. Animals heal after wounding.

When trees are injured and infected, processes of boundary formation start. Trees do not restore or repair wood that is injured and infected. In this sense, trees do not heal. Instead, trees compartmentalize wound infections.

Compartmentalization is the tree's best defense process after injuries where boundaries form that resist the spread of infections. The boundaries also protect systems involving water, air, energy storage, and mechanical support. In a sense, the boundaries are like an inside bark.

To support their massive systems for long periods, trees require high amounts of energy. Trees trap more of the sun's energy than any other groups of organisms. In a sense, trees are like big batteries, the biggest on earth.

Trees use energy very efficiently with almost no waste. They pass energy on to many associates, and the associates provide many benefits in return to the trees. Trees help soils to remain healthy.

Trees, as big batteries, store energy as insoluble starch and oils in living cells in the wood of branches, trunks, and other woody roots. The wood itself is a form of stored energy for other organisms because cellulose is made of of long twisting chains of glucose--sugar.

In animals, a process of programmed cell death regularly takes place. Dead cells are broken down and eliminated. Other processes form new living cells in the same positions of those that died. Animals are regenerating systems. Regenerating means new cells form in old places.

Trees are generating systems. Generating means new cells form in new places. In trees, the woody framework consists of highly ordered connections of living and dead cells. Some dead cells function for liquid transport. Other dead cells maintain mechanical support, and hold water. Unlike animals that are constantly replacing dead cells, trees incorporate dead cells into their framework.

Trees regulate their growth within the limits of available energy, water, elements, and space. Trees do not grow beyond their means. Trees use and shed leaves and needles, reproductive parts, nonwoody rots, and dead twigs, branches, and woody roots.

Trees in nature are connected with each other and with many communities of other organisms in ways that ensure long-term survival for the trees and their associates. This system is called a natural forest.

Some correct planting procedures for trees

1. Select healthy trees. Do not buy or plant trees that have roots crushed or crowded in a bag or container.
2. Plant properly. Do not plant too deep.
3. Plant the right tree in the right place. Do not plant large-maturing trees near buildings or power lines.

Select healthy trees

Money is wasted when you buy or plant trees that have roots crowded or crushed in bags or containers. Check roots before you buy or plant. If only a few roots are crushed, remove them with a sharp cut.

Plant properly

DO: Plant at the depth where roots spread from the trunk. Prepare a planting site, not just a hole in the ground. Loosen the soil far beyond the drip line of the tree. Brace the tree only if it will not remain upright in a moderate wind. If necessary, brace only with broad, belt-like materials that won't injure the bark. Mulch away from the trunk with composted material (mulch should not touch trunk). Keep soil moist, not water-logged, to the depth of the roots. Remove dead and dying branches. Wait until the second growing season to begin training cuts for shaping and to begin fertilizing.

DO NOT: Do not plant to deep. Do not bury roots in small deep holes. Do not wrap trees. Do not amend the soil, unless the soil is very poor. Do not brace the tree so tightly that the tree cannot sway. Do not brace with wire in a hose. Do not fertilize at planting time. Do not plant grass or flowers near the tree. Do not remove branches to balance crown with roots.

Plant the right tree in the right place

DO NOT plant large-maturing trees near buildings or power lines. Money is wasted when trees are topped or mutilated later. If a tree must be planted near power lines, plant only dwarf or low, compact species or varieties. Talk to knowledgeable people about the many choices you have for trees that have mature shapes and sizes that will fit your planting site.

About the Author

Dr. Alex L. Shigo is considered by many to be one of the foremost authorities on trees in the world today. Retired from the U.S. Forest Service, he is an internationally recognized researcher credited with the development of expanded interpretations of decay based on compartmentalization and microbial succession. His research includes over 15,000 longitudinal tree dissections with a chain saw. He has published over 15 textbooks used in many universities worldwide. For more information about seminars and to order Dr. Shigo's publications, contact: SHIGO AND TREES, ASSOCIATES, P.O. Box 769, Durham, NH 03824, USA. Phone: 603-868-7459; Fax: 603-868-1045.

Original Source

This excerpt is adapted from Tree Basics and 5 Minute Tree Care with the kind permission of the author. The full text, including numerous photographs and figures can be purchased from Shigo and Trees, Associates, P.O. Box 769, Durham, NH 03824, USA. Phone: 603-868-7459; Fax: 603-868-1045.

Related Editions to The Overstory

• The Overstory #43--Essentials of Good Planting Stock
• The Overstory #19--Selected Tree Seed
• The Overstory #1--Sheet Mulch