Posts Tagged ‘root structure’

All trees are sensitive to root disturbance. Examples include construction, over watering, sprinkler instillation, and grade changes. The effects of these changes on pre-existing trees can take five to ten years to become fully visible.

To understand how trees are affected by root disturbance, it is important to understand the structure of a tree’s root system. Ninety percent of the root system is located in the first eighteen to twenty-four inches of soil, and the roots extend radially from the trunk one to two times the height of the tree.

Root Disturbance - Example Of Irrigation Installation

During construction, the root system is cut to install foundations, sidewalks, driveways, and landscape beds. The closer to the tree the construction occurs, the more destructive it is. Damage also occurs through compaction of the soil from heavy equipment repeatedly driving over the root zone. Clay soils compact more easily than sandy soils. Compaction of the soil reduces the pore space between soil particles, eliminating the oxygen in the soil, causing root decay. Further damage results from utility lines and irrigation systems being installed. Sprinkler instillation can cause just as much damage as initial construction due to the amount of trenching in the root zone.

Watering the new landscape can then cause even more damage. Most of our native trees are adapted to dry sites and are used to receiving natural rainfall (30” of rain a year). When an increase in water occurs, the soil can stay saturated, eliminating the amount of oxygen. Roots then begin to rot in this anaerobic condition, and the tree begins to decline or die. Clay soils stay saturated longer than sandier soils.

It is recommended to limit watering to 1” of water a week during the growing season including rainfall. This will allow the soil to be moistened and dry out, mimicking this region’s natural rainfall pattern.

Remember slope, drainage, natural rainfall, and sun exposure will vary the frequency and duration of the sprinkler system schedule.

Improvement of the soil through fertilization is recommended to encourage new root growth. Fertilizing three to four times a year for the first few years following root damage is common. Root regeneration can take many years, do not expect quick results.

A systemic insecticide can be added to the spring fertilizer application to reduce insect feeding. Borers commonly attack stressed trees causing significant and irreversible damage. Active damage can be recognized as weeping fluid or sawdust on the trunk, but it is not always visible. Systemic insecticides cannot be applied to fruit trees such as Pecans, Walnuts or Peaches.

Because trees are stressed following construction, pruning should be minimal the first few years. The more leaves and branches in the tree, the more food the tree can produce aiding in recovery. Branches causing clearance problems with houses, driveways, or streets can be pruned.

When trenching to install a sprinkler system, stay as far from the trunks as possible, preferably outside of the canopy drip line. Commonly a combination of rotary heads along the perimeter of the yard and popup heads in the landscaping beds works well. If trenches must be dug under the tree’s canopy, try trenching radially towards the trunk instead of across the root zone.

Base Investigation and Clearing Root Flares Using the Air-spade_®

The Air-Spade is a handheld soil excavation tool connected to a large air-compressor. The high pressure stream of air is funneled through a small nozzle breaking dense soils apart into small particles. By using air to excavate soil, delicate roots, underground pipes, and hard surfaces are not damaged. Arborists can recommend using the Air-Spade for many reasons.

Air-Spade Uses

• Expose root flares of trees planted too deep
• Expose root flares of trees covered with fill dirt
• Expose root flares and root structure 6” to 18” below grade for base investigation
• Expose root flares for Macro-Injections
• Digging trenches without cutting roots or concrete

The root flare or root collar is the area where a tree begins to flare outward at ground level. This is a critical part of the tree where trunk tissue changes into root tissue. If this area is covered with soil and kept moist for extended periods of time, the tissue begins to breakdown. This leaves the tree vulnerable to root decay and ultimately poor health and vigor.

Base investigation is needed when an Arborist suspects deterioration of root tissue. Since roots can not be seen above the surface, the only way to confirm this suspicion is to excavate the soil and inspect the root structure.

Clearing root flares for Macro-Injections is another common use for the Air-Spade. Macro-Injection is an application method used to apply chemicals such as Alamo for Oak Wilt management. Soil and debris are removed quickly and easily without damage.

EXPECTATIONS OF AIR-SPADE WORK

1. Preparing the Soil Water the soil area around the tree one or two days prior to the Air-Spade work being done. This will soften the soil and expedite the process.
2. Clearing the Work Area The work area around the tree will need to be prepared. Prior to the movement of soil, we will remove any grass, ivy, shrubs, or flowers from around the base of the tree. This work area is typically one to two feet from the base of the tree. We do not preserve the vegetation in most cases and request you salvage any plant material you want to keep. We do not replace the vegetation removed.
3. Noisy Process Due to the high pressure air being used and the compressor needed, the process can be quite noisy.
4. Backfilling the Excavated Area When excavating a root flare the void created can sometimes be quite deep. If the area can not be left open, it can be filled with coarse mulch. When the area exposed is greater than eight inches deep, medium to large stone can be used backfill the area insuring greater air circulation around the base.