Posts Tagged ‘root’

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.

A Significant Root Pathogen

Ganoderma lucidins, the varnish fungus, is a pathogen that enters openings in root systems of many tree and shrub species. In our region, Red Oak, Cedar Elm, Pecan, Live Oak, Pears, and Photinia have all been reported to be species commonly infected by this fungus.

The entry points can be from any activity that damages or severs a plants root system. The fungus lives in the soil as a saprophyte, that is to say, it can live on dead organic matter with no ill effects until it encounters live roots that have been cut.

Published literature, archaic as it may be, suggests the fungus colonizes a plants root system slowly and may take several years, 10-20 has been proposed, to finally kill a tree or shrub. Some have theorized that is might just be a natural component of many old tree species.  We feel that it may be quite a bit more aggressive than first thought. Regardless of the pathogens history, it causes significant damage to our shade trees by destroying a trees structural root system.

Trees have two primary root systems. The structural root system is responsible for anchoring a tree to the earth. A trees fine feeder root system is responsible for the daily demands of moisture and nutrients. Once the structural root system has been compromised, a trees stability becomes quite a concern. Often, trees that fail during storms show evidence of colonization by Ganoderma sp.

The fungus will produce a fruiting structure, a fungal conk, near the base of the tree. It is a shelf like structure that varies in color from a rusty orange-red to a dark red with cream coloration almost always shiny in appearance. The concern is that once the fruiting structure is evident, the fungus has often destroyed a large part of the trees ability to stay anchored to the earth, thus creating a high potential for failure and a potentially dangerous situation.

The difficulty is that above ground signs can mimic other problems. Trees infected with Ganoderma sp. often leaf out in the spring with significant dieback and large dead branches with no changes in the trees environment. Tree owners will often report that the tree looked fine last fall. Even at this stage of the infection, there may be no visual evidence, a fungal conk, apparent at the base of the tree. There is also the opposite scenario in that a trees canopy looks perfectly fine, but fruiting structures have developed. In either case, further investigation may be recommended. These recommendations should never include anything that is proposed to help or control the infection. Recommendations should be to immediately investigate a potion of the trees below ground structural root system to determine the extent of structural root loss.

The sad conclusion is that there is no prevention or control once a root system has been colonized. There is obviously the avoidance of root damage of any type, which is very unlikely in the urban environment. The positive aspect is that after investigation, immediate removal is not always necessary. It does give your Certified Arborist a baseline mark to make appropriate recommendations regarding a potential timeline for removal and replacement.

This is not anything new to our urban forest, nor is it any type of epidemic that all susceptible tree and plant species will die from. It is a serious concern if a large.

by Kevin Bassett and Russell N. Peters

What is deep root fertilization?

Deep Root Fertilization - Injection

Deep root fertilization is a process where a high quality nutrient solution is injected into the root zone of trees. The materials are injected into the root zone under pressure which helps aerate or provide much needed oxygen to the root system. The soil injection begins just below the surface and goes to a depth of twelve to fourteen inches. Soil injection sites are placed two to three feet apart in a grid pattern under the canopy area and beyond the drip line.

Normally, fertilization programs should be repeated once or twice a year. There will be instances where severe root damage has occurred, soil compaction exists, or other health problems are present. In these instances, it may be recommended to increase the frequency in order to improve conditions in and around the root zone which can improve overall health and vigor.

Roots are opportunistic and develop where ever oxygen, nutrients, and moisture are present. Ongoing deep root fertilization programs improve the oxygen content, microbial activity, and nutrient levels within the soil, leading to improved environmental conditions around and within the root zone.

The formulation of our fertilizer is a custom mixture manufactured by Plant Health Care, a leading manufacturer of organic solutions for trees, shrubs and turf grass. The contents of our mixture is listed below.

There will be times when your Arborist will recommend amendments to the standard mixture when certain nutrient deficiencies or health concerns are present.