Maintenance & Irrigation
Blog Post by Kerry Norman
These two procedures, I believe, are the most critical factors in the success and survival of relocated trees. Trees are particularly sensitive to soil moisture levels, following the loss of often more than 80 percent of the root system. The need for supplemental water greatly increases due to the reduced capacity of the remaining root system to absorb water. Initially, the root ball soil provides the only reservoir for water until the roots begin to grow into the native soil. Trees that usually survive without water for long periods now require regular and frequent irrigation, resulting in an increased risk of soil pathogens.
A fine balance between soil that is too wet and too dry must be maintained. This can only be achieved by regularly scheduled servicing by experienced staff, usually supervised by a certified arborist. Although the practice of irrigating a tree may sound simple, great care and effort is required to insure proper soil moisture. It is imperative to check soil moisture by using a soil probe before and after watering to determine how much water if any to add. “Monitoring of soil moisture can be scheduled, the actual irrigation cannot”. Two of the most common problems are over or under watering.
In my opinion, the most serious threat to the survival of relocated trees is over-watering. I would rather see irrigation error on the drier side. Over-watering usually occurs when the tree is either planted below grade or the soil grade has been increased around the tree. These conditions frequently result in serious problems. Other conditions that are associated with over-watering include broken irrigation lines, planting in poorly drained soil and at the base of a slope.
Under- watering most often occurs when the irrigation water does not percolate readily into the root ball, this most commonly happens as water runs over the top of the root ball and into the backfill. Consequently, the soil within the root ball remains dry because the water in the backfill does not move readily into the root ball. Soil watering basins must be maintained just inside the edge of the tree root ball to ensure percolation. Mulching, which reduces soil temperature and helps conserve soil moisture, is conducive to new root growth as newly developed fine roots are highly susceptible to desiccation.
One of the key pitfalls related to maintenance is that contractors, developers, homeowner’s etc., rarely budget for post-relocation tree care. Problems requiring immediate corrective action are likely to develop without a maintenance program and regular monitoring. It may be too late by the time someone recognizes the problem. I’ve found that about 70 percent of the failures in relocating trees are attributable to inadequate maintenance. Adverse site conditions, construction-related problems and undetermined causes are responsible for the other failures.
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