Landscaping services continue to grow in an ever-expanding range of goods and services, as contractors are constantly looking for new and better ways to serve their clients. One value added service that has gained prominence nationally in the last few years is irrigation system installation. The idea is that, by installing the irrigation system, the owner of the landscape will prevent losses during dry periods and save time when watering is needed. Landscapers like irrigation installations because they are fairly easy to install without a lot of special equipment. Help the homeowner by helping him take care of his trees and shrubs - simple and straight forward right. This idea works great if no mature trees exist where the irrigation system is to be installed. However, big, beautiful, majestic, mature trees are unintentionally killed when unknowing or uneducated installers encroach upon the trees?EUR??,,????'??? most neglected structural element, its roots. Some landscapers think they are digging trenches to help these big old trees survive in the harsh urban environment. They don?EUR??,,????'???t realize that they are digging tree graves. By cutting off the trees water and nutrient supply, the tree slowly declines and eventually dies. The problem is that some irrigation system designers and installers don?EUR??,,????'???t understand the biology of trees. Tragically, there are many misconceptions and myths about how trees grow and what they need to thrive in the landscape. This article will help you identify some anatomical structures of trees and give you some sense of how these are important to a trees?EUR??,,????'??? survival. The article will also explain how to modify irrigation installation to accommodate those particular spatial needs of trees, giving your clients that value-added feature of tree safety. Trees are big and they need a lot of space both above and below ground. Contrary to many textbooks, the root system of a mature tree is not a mirror image of the canopy - with large roots that grow deep into the soil - and there is typically no taproot. On the contrary, roots larger than four inches only exist within four feet of the buttress. A tree growing in a natural environment can have a very extensive root system. Roots and root graft networks can extend for hundreds of feet from the trunk of a tree growing in a natural forest environment. In urban settings, roots are less complex and are more easily defined. Generally speaking, the important roots of the urban tree exist directly under the canopy. In Arboriculture, we call this area the ?EUR??,,????'??drip area.?EUR??,,????'?? There are basically three kinds of roots in this area; structural, absorbing and buttress roots. Let?EUR??,,????'???s look at how the tree uses these roots and how irrigation system installation can cause problems. STRUCTURAL ROOTS These roots are one to four inches in diameter and form a network of cables that weave and curve in the soil within the drip area of the tree. They grow four to 10 inches below the soil surface and function as anchors to hold the tree upright. They also serve as a storage facility for plant food (starch), and they are the conduits that transport nutrients and water from the absorbing roots toward the bole (trunk) of the tree. If a large enough proportion of these roots are injured, catastrophic root damage occurs. Installing irrigation too close to the trunk can compromise the structural integrity of the tree. This means that if you trench too close to the tree, the tree could fall over and you would be liable for the damage. Severing these roots also cuts off some of the water and nutrient pathways and can result in decline or slow death. Decline and slow death may take many years to kill a tree. Even so, you would still be liable for any damage or loss of value that occurs as a result of trenching too close to the trunk. BUTTRESS ROOTS If you draw a circle with a circumference of exactly four feet from the trunk of the tree, the roots inside this circle go from being large trunk sized to smaller baseball sized roots. In arboricultural terms we call this area the Zone Of Rapid Taper (Z.O.R.T). If more then four roots within this Z.O.R.T. are severed with trenching equipment, the results will be catastrophic. Decay organisms will easily enter the buttress and the structural integrity of the tree support system will be compromised, even to the extent that the tree will be in immediate danger of falling over. If trenching or other heavy equipment excavation must be performed within the Z.O.R. T., tree removal is highly recommended, especially if there are hazard targets within the fall radius the tree. ABSORBING ROOTS These fine, hair-like roots do not grow deep in the soil. In fact, these roots only grow in the top six inches of soil and increase in numbers as you get closer to the soil surface. They also get more plentiful as you get nearer to the root flair (buttress). These roots and their corresponding mycorrhizae (symbiotic fungi & roots that form absorbing, hair-like structures) take up roughly 95 percent of all nutrients absorbed by the tree. Although these roots do not store food or provide structural support for the tree, they are the most important roots in the transport of nutrients. These roots are highly sensitive to soil disturbance or soil compaction. We have now covered the problems associated with trenching to close to trees, so lets look at some alternative installation techniques that will have less impact on the roots and offer your customers value-added safety. Air Excavation In this simple technique, HP Air is used to dig up soil, leaving woody roots intact. Using this technique is much easier than traditional excavation. When the proper depth is achieved, irrigation lines are placed under the roots and amended backfill is used to complete installation. Although the local absorbing roots are killed by this treatment, structural and buttress roots are unaffected. Since the tree can easily regenerate new feeder roots after this treatment, the impact is much less severe. Tree professionals prefer this method because of its ease and aeration benefits to the tree. Tunneling Another option is to tunnel under the root system the same way that gas lines are installed under streets. This method causes no traumatic problems for the tree and increases soil drainage. Although specialized equipment is needed, the cost of the equipment is far less than the cost of catastrophic tree failure. Besides, your service will be even more valuable to your clients when they realized that you go to extraordinary efforts to avoid damaging beautiful, valuable, irreplaceable mature trees. Every situation is different. If trenching or other construction must be performed near the bases of large mature trees, you need to have a consulting arborist examine the plans and the trees. The consulting arborist will draw up specifications that will ensure trees are not adversely affected by construction. Marty Shaw is a member of the American Society of Consulting Arborists. He is an ISA Certified Arborist, a Tennessee Certified Nursery & Landscape Professional, a Licensed Horticulturist, and is President of TIPCO, Inc. in Knoxville, Tenn.