The Below excerpt is from an excellent book "Your Florida Landscape" by Robert J. Black and Kathleen C. Ruppert. This book contains rich resources for anyone interested in knowing about anatomy about trees, how tree root works and how to take care of different root systems. This books also deals with tree structures and tree pruning techniques. Anyone wanting to know more about tree removal or stump removal and want to prune thier tress should read this book.
THE TRUTH About Trees
Numerous misperceptions about trees and their care abound and are passes around. Following are some truths about trees and tree care which include discussions bases on current research finding.
Tree Roots Most Trees do not have taproots.
The deep roots that grow directly beneath the trunks of some trees are known as taproots. Taproots may develop on some trees in the woods in well-drained soils. Taproots generally do not form on trees planted in urban landscapes nor do they develop when the soil is compacted or the water table is close to the soil surface. Some oaks and pines will develop taproots when planted in sandy, well-drained soils.
Roots grow far beyond the edge of the branches.
A tree growing in the woods has a root system reaching well beyond the outer perimeter of its branches, often to a distance from the trunk equal to the tree’s height. Roots on trees and shrubs planted in a landscape grow to about 3 times the branch spread within 2 or 3 years after planting.
Damaging roots on side of a tree may cause branch dieback wither on that side only or at random throughout the crown.
Unless the trunk is twisted, roots on one side of a tree such as oak or mahogany generally supply the same side of the crown with water and nutrients absorbed through the roots. When roots on one side of a tree are injured, branches on that side will often drop leaves. When trees such as the maples and rosewood receive damage on one side of the roots system, branch death may occur anywhere in the crow of the tree.
Root pruning does not stimulate root branching all the way back to the trunk.
Roots are often pruned before moving a tree in hopes of creating a denser root ball. However, most root growth after root pruning occurs at the end of the root just behind the root pruning cut, not further back toward the trunk. This means that you should dig the root ball of a recently root pruned tree several inches beyond where it was root pruned. If root pruning will be conducted only once before transplanting, do it 6 to 10 weeks before moving the field-grown or landscape tree. Some quality tree nurseries root prune each year to prepare a tree for transplanting.
Roots circling around inside a container do not continue to grow in a circle once the tree is planted in the landscape.
Unless the container is specially designed, roots frequently circle within the perimeter of a container several times before the tree is planted into the landscape. The portion of the root which grew in the container does not straighten out, but new growth on this root will usually not continue to circle. Circling roots should be cut at planting to prevent eventual girdling and strangling of the trunk.
Most roots are in the top 3 feet of soil. The finer roots are concentrated in the top foot of soil.
Most tree roots are located within the top 3 feet of soil. In well-drained soil, some roots grow 10 feet or deeper directly beneath the trunk. However, because the majority of the fine roots are concentrated in the top foot of soil, minor soil disturbances can injure or remove a large portion of the absorbing roots on a tree. Especially vulnerable are trees growing near construction sites.
Construction Around Trees
Injuries inflicted by heavy equipment during construction (or at any other time) can cause major and permanent damage to the tree.
Because a tree does not replace injured tissue (heal) like an animal does, a wound or injury to its trunk, branches or roots permanently reduces the tree’s capacity to find off insects, disease or other potential stresses. Many roots are destroyed when heavy equipment operates over the root system with q bulldozer, earth scraper or other piece of heavy equipment can cause significant root damage. Equipment should not be permitted to operate within the dripline of trees which are to be saved.
To save a tree during construction, do not disturb soil beneath the branch dripline.
Because 50% of a tree’s root system is located between its trunk and its dripline, sturdy fences should be constructed at the dripline to prevent equipment and vehicles from operating in or crossing over this sensitive area. Tree roots extend much further than the dripline. However, it is usually not practical to protect the entire root area. Protecting the area within the dripline ad good irrigation management are the most important measures in helping prevent construction related tree decline.
Grading to prepare a site for laying sod or planting shrubs can harm trees.
Since many of a tree’s fine roots are located close to the soil surface, changing the soil grade by as little as 6 inches can cause extensive damage to its root system. Design you landscape to fit the existing grade. If significant grade changes must be made close to a tree, the best course may be to remove the tree and plant several younger, healthy trees. However, a certified arborist may be able to devise a system to save trees on construction sites.
Building a tree well around the trunk of a tree will not help save a tree from the effects of fill soil.
Never remove soil from or add a large amount of soil to the area within the dripline of a tree. Three or four inches of soil can be added to small areas under the tree provided the added soil has a coarser texture than existing soil. Building a wall (commonly called a tree well) several feet from the trunk then adding more than 3 or 4 inches of soil outside the well often kills the tree by suffocating most roots growing beyond the tree well. If a tree well is to be the used construct it no closer to the tree than the dripline and grade the soil outside of the well to prevent runoff water from entering the well. Success has been reported in several case where gravel was spread over an existing grade and vertical vent pipes were installed every 10feet to supply the roots with oxygen. Coarse textured fill soil was then carefully spread over a soil-separator fabric that had been placed over the gravel. Hire a certified arborist to conduct this specialized work.
If a tree survives the first 2 to 4 years following construction, it may still die from construction related injuries.
Trees may decline quickly or slowly after construction of a building. 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 period. Even if a tree does not show obvious signs of decline for many years, branches may quickly lose leaves and begin a rapid decline following a drought period. A year or two later, the tree may be dead.
Tree Trunk and Branch Structure
A trunk with a crook in it is just as strong as a straight one.
Trunks with slight doglegs, crooks or bends are not weaker than those which are straight. This is a normal development on many trees, especially oaks. Healthy trees will grow out of this condition, and the trunk will appear straighter as it grows larger in diameter.
Branches that remain smaller than half the trunk diameter are more securely attached to the tree than are larger branches.
Branches growing in a horizontal orientation are usually smaller in diameter and well secured to trunks. Branches with diameters that are large in proportion to the trunk can become poorly attached. A branch growing in an upright manner parallel to the trunk becomes a second trunk, and the tree is said to have a double leader. Double leaders often form included or embedded bark in the crotch. This can be dangerous because the tree can easily split during a storm.
Topping a tree creates a dangerous tree.
Topping or rounding over is the practice of shearing off the top of a tree, thus removing branches and stems without regard to tree structure. Topping creates a hazardous tree because the wood inside the cut branch begins to decay. The cut stub is open and susceptible to decay organisms. The sprouts which grow in response to topping are not well secured to the topped branch, and they can easily split from the tree as they grow larger. When reducing the size of a tree, use a technique called drop-crutching. This involves pruning a branch back to a living branch that is at least half the diameter of the cut branch.
A tree with multiple leaders (trunks) can become hazardous to people and property as the tree grows larger.
Never allow larger maturing trees to grow with multiple upright leaders. These trees may look handsome when young but can become hazardous as they grow older. Always prune large-maturing shade trees so that leaders or branches are spaced 18 to 36 inches apart along the main trunk.
Trees do not heal, but they are capable of isolating injured tissue from healthy wood.
When trees are injured, they do not replace the cells lost in the injury. The swollen callus tissue developing around a trunk wound or pruning scare is simply closing over the injured tissue, not healing it. In order to stay alive, a tree must seal off injured tissue from its healthy portions. The storage capacity and functions of the injured parts are forever lost. Additional injuries seal off more wood, which further reduces the supply of available energy and can the tree to slowly starve.
Never make a flush cut.
Though standard practice was once to prune a branch flush with the trunk, extensive research has shown that this practice injuries the trunk, is extremely detrimental to tree health and shortens a tree’s life. Flush cuts make a tree more susceptible to frost cracks, heat injury, root problems, cankers and sprouting. Always cut to the outside of the branch collar. Usually located at the base of the branch and easily see, the collar is the swelling where the branch meets the trunk. When properly done, a branch can be removed in its entirety without injury to the trunk.
Rapid, thick callus growth around a pruned branch does not indicate the branch was pruned properly.
The callus forming around a pruning scar often forms rapidly, regardless of the pruning technique. This tissue should form a ring or donut-shape if the branch was removed properly. If the callus is elongated or oval-shaped, the branch may have been pruned too closely to the trunk. Despite rapid callus formation around a pruning cut or injury, extensive wood rot can develop inside the tree.
Wound dressings and pruning paints do not prevent wood rot.
Wound dressings do not prevent wood decay behind a pruning cut. They provide no benefit to the tree. Some research indicates that would dressing actually promote decay in certain situations. If pruning paints or wound dressings are to be used for cosmetic purposes, apply only a very thin coat. Only proper pruning practices prevent wood rot.
Trees should be planted no deeper in landscape soil than they were in the nursery.
Trees and shrub should be planted at the same depth or slightly higher than they were in the nursery field soil or container medium. This allows for the quick root growth crucial to tree and shrub establishment. Planting too deeply slows root growth which can lead to poor establishment or death.
Transplanted trees do not benefit from amending the backfill soil.
The soil removed from the planting hole should be used to fill in around the root ball. No amendments need to be added to the backfill soil, since it does not improve survival or growth after planting. After transplanting, apply a layer of mulch 2 to 3 inches deep around the base of the tree and out the dripline. Pull mulch back 2 to 3 inches from the tree trunk.
Tree should not be pruned at transplanting to compensate for root loss.
Pruning shoots and branches to compensate for root loss on transplanted trees is not recommended. The signal that initiates root regeneration originates in the shoot tips. Pruning removes shoot tips and can reduce root regeneration. Begin corrective pruning 1 year after planting. Correct major structural defects at planting if the tree will not be pruned for several years.