Institute of Food and Agricultural Sciences
Hendry County Horticulture News
Trees - Many Lost or Damaged Due To Misconceptions
"Nice trees," "Beautiful wooded lot accented with oaks, pines and cabbage palms," "Big oaks," "Hidden hammock," - read the real estate listings touting the natural beauty imparted by trees. Without a doubt, trees impart real value to a property and constitute one of the attractions of living in Hendry County. Trees are the fundamental building blocks of creating a successful landscape design. They serve as the framework on which landscapes are built. On heavily forested lots creating an effective landscape may be a simple as adding a few shrubs and other plantings among existing trees.
Trees are not only givers of shade, their diversity of form, floral colors and leaf shapes add visual interest to plantings. They help filter the air we breath removing tremendous quantities of dust and pollutants, while absorbing carbon dioxide and releasing oxygen which is needed by humans and animals alike. Trees provide habitat for wildlife and create micro climates for the benefit of other plants. They cool the surrounding environment and help intercept and retain falling rain. Numerous scientific studies have indicated that trees impart a feeling of well being in people and have demonstrated that even crime and vandalism can be affected by the presence or absence of trees. Without a doubt, most people would elect to live in a neighborhood nicely planted with mature trees over a barren leveled area if given a choice.
Although most folks would agree on the value of trees. There are many misconceptions about trees and their care. In many instances, these misunderstandings actually harm the very trees that people hold dear and have spent considerable resources to obtain.
In sandy, well drained soils some trees such as oaks and pines may develop deep roots directly beneath the trunk. These are commonly called tap roots. When the water table is close to the soil surface or when the soil is compacted, tap roots do not develop. Tap roots generally do not form on trees planted in our urban landscapes. In our area, we find that most tree roots are located within the top 36" of soil. In addition, contrary to popular belief, root systems reach well beyond the edge of the branches. Frequently, roots extend from the trunk as far as the tree is tall. Roots on trees and shrubs planted in a landscape frequently grow to 3 times the branch spread within 2 or 3 years after planting. Approximately 50% of the root system is located outside of the drip line.
Because the majority of the fine roots are concentrated in the top several inches of soil, minor soil disturbances can injure or remove a large portion of the absorbing roots on a tree. This often happens in landscapes surrounding recently constructed buildings. Many roots are destroyed as heavy equipment operates over the root system. Even one pass over the root system with a bulldozer, earth scraper or other piece of heavy equipment can cause significant root damage.
A small trunk wound inflicted by heavy equipment during construction or at any other time can cause major injury to the tree. Since trees cannot replace injured tissue (heal) like animals, injury permanently reduces the trees capacity to fight future stress caused by insects, disease or other factors. To save a tree during construction, do not disturb soil beneath the branch drip line. No equipment should operate within this area if the tree is to be saved. Sturdy fences should be constructed at the drip line to encourage enforcement of this guideline. This serves as the best guide to helping prevent construction related tree decline.
The addition or removal of soil around the base of a tree may seriously disturb the delicate relationship between roots and soil and may considerably damage or kill the tree. In many areas, fill is often added to a building site and no precautions are taken to minimize the shock of placing the roots in a new environment.
When fill is added over existing soils, air and water, which are essential for normal functioning of the roots, are partially excluded. As a result, the roots die and the symptoms become visible in the above ground parts. The visual symptoms are small yellow leaves, numerous suckers along the main trunk and branches, many dead twigs and in some cases, large dead branches.
The extent of injury from fills varies with the kind, age and condition of the tree; the depth and type of fill; drainage and several other minor factors. Maple, oak and evergreens are most seriously injured, while elm, ash, willow, sycamore and locust are least affected.
The deeper the fill, the more marked is the disturbance to the roots. Clay or marl fills cause most injury because the fineness of the soil shuts out air and water most completely. The application of only an inch or two of marl soil may cause severe injury. Sandy fills may be added to a depth of four inches. As a general rule, the application of a layer of few inches of the same type of soil in which the tree has been growing, will do no harm providing that compaction from equipment movement does not occur. The roots will eventually become accustomed to the new situation by producing additional roots near the surface.
Trees frequently decline after fill and construction operations. Often, branches begin dying within a year or two due to severe root damage. The tree may be dead within 3 or 4 years. However, it is not uncommon for trees to show a slow decline over a 5 to 15 year period. The tree may not show obvious signs of decline for many years, but, following a drought period branches may quickly loose leaves and begin a rapid decline. The tree may be dead a year or two later.
All to often, valuable trees are damaged or lost due to the activities of well meaning owners, who have purchased a parcel for it's trees, but have little awareness of the biology of trees and how to protect them during land clearing and construction. While little can be done to save trees that have been suffered from grade fills or construction injury, awareness of these problems can help save many valuable trees. Good luck and good gardening.
Gene McAvoy is the horticulture agent with the Hendry County Extension Service. Direct your horticulture questions to PO Box 68, LaBelle, FL 33975, e-mail - firstname.lastname@example.org or phone 863-674-4092 or 863-983-1598. You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle. Office hours are from 8:00 - 5:00.
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