Trees are important to effective landscapes, but simple actions can damage their health and longevity. Unfortunately, many myths exist about the management and treatment that trees need. Three common contractor operations plagued with myths that damage trees are construction activities, and selecting and transplanting trees. Construction Activities Soil compaction, changing and leveling the grade, changing the drainage patterns, excavating and trenching, operating heavy equipment, disposing of chemicals, burning debris, and the stockpiling of topsoil are typical construction activities. The types of damage to trees can occur in four main ways: root zone compaction; mechanical damage to trunks and branches; mechanical damage to roots; and chemical and material spillage at some sites. The root system of trees is the key to their survival. At construction sites, protecting tree roots is the most important step to keeping your remaining trees healthy. Unfortunately, most people do not understand tree biology, and may have mistaken ideas about tree growth. Some of the most common myths that can lead to damages associated with construction activities are highlighted in this section. We list specifications to correct the myths and a set of Site Parameters (Table 1) for protecting trees from damage prior to and during construction activities. Myth 1: Tree roots exist only under the tree canopy, or out to the drip line. Tree biology: Tree roots extend well beyond the drip line of the canopy, often two or three times farther. During construction, just protecting the tree trunk is not enough to prevent equipment and trucks from squishing the soil in the root zones. Specification: A sturdy root zone protection barrier (Figs. 1 and 2) should be installed at the drip line. Placing the protection zone two to three times past the drip line would be much better. (Table 1). Myth 2: Tree roots grow deep into the soil and thus are protected. Tree biology: All roots need oxygen to survive. Heavy clay soils and soils compacted by traffic have little air space so roots must stay in the upper levels to have enough air to survive (Fig. 3). If construction activity squishes the soil, it closes the air pores and this will cause existing roots to suffocate and die, or be damaged. Specification: If constant traffic must cross the root zone, build a protective bridge using railroad ties to support steel plates. Damage from temporary traffic may be prevented by using metal traffic mats, or by using an 8- to 12-inch thick mulch layer to damper the compression (Fig. 4). When frozen, soils will suffer minimal compaction by traffic. Myth 3: Tree roots are woody and tough. Tree biology: Large structural roots near tree trunks are tough, and they help support and anchor the tree. But the small, fleshy roots at the outer reaches of root zones are tender, and they gather most of the water and nutrients needed for healthy trees. Excavation and topsoil removal activities that cut roots will prevent trees from absorbing critical supplies of water and nutrients. Specification: (see Table 1) Precautions are needed for even shallow excavations. Myth 4: A little trench won?EUR??,,??t hurt. Tree biology: Any trench, even a narrow slit, penetrating below the roots near a tree trunk will destroy up to 45% of the tree root system. Specification: Detour around and outside of the drip line of trees (most pipe is flexible, so why are straight lines so critical?). OR: Require hand trenching or the use tunneling or directional boring to protect roots under the drip lines. Myth 5: Damage to tree roots will affect tree growth immediately. Tree biology: Trees have food reserves stored in their branches, trunks and roots that they can use to survive construction damage. It may take two or three years before trees begin to show symptoms of decline (Figure 5). It may be five to ten years before property owners notice and call an arborist to ?EUR??,,??save their trees.?EUR??,,?? By then the building contractor is gone and seemingly not responsible, but the cause of damages may still be proven in court. Specification: Specifying and enforcing proper Site Parameters (Table 1) may protect contractors from potential liability. Myth 6: ?EUR??,,??As long as I stay five feet away from the trunk, the tree won?EUR??,,??t be damaged.?EUR??,,?? Tree Biology: Tree trunks and branches are tough, and they can tolerate some damages. You have probably seen trunks with large scars from being scraped by bulldozers, and branches broken by backhoe booms (Figs. 6 & 7), and the tree has not died. But trees whose roots have been damaged or compacted will begin to decline in health, and may eventually die if not treated. Prevention: Follow the Site Parameters (Table 1) to protect your trees from construction damage. Contact a Certified Arborist for suggestions specific to the site before construction begins (most of us would be pleased at this), or to treat trees that may have suffered damage from construction activities. Some trees are highly susceptible to construction damage and should be considered for removal unless strict attention to protection details is possible. Susceptible trees are: beech, yellow poplar, hickory, birch, some oaks, most maples, and all conifers. Tolerant trees are: elm, poplar, willow, plane tree, and locust. Selection Criteria Myth 7: All trees can grow at all sites. Tree biology: Different trees have different growth requirements, creating a complex series of factors for you to consider. The main considerations are the desired function, the intended location, the hardiness, the mature size and shape of the tree, the soil conditions at the site, potential pest problems, and the grower or source of the tree. Usually, reputable sources will sell only trees that will survive in your area, but sites such as lower elevations or open and exposed areas may cause problems. If you have peculiar conditions, describe them to your source and get an expert opinion. Consider the type of soil and especially the water drainage conditions of the site. Collect a soil sample from the anticipated root zone and have it tested for pH and fertility. The test results will give you recommendations for adjusting each to benefit the tree. Myth 8: All trees sold at nurseries and garden centers are good specimens. Tree biology: This is hardly the case. You must be a good buyer, which, fortunately, is not hard to do. 1. First, look for a trunk flare at the base of the trunk and examine the root mass, if possible (Figs. 8 & 9). The base of the trunk should flare out like your palm flares out from your wrist. 2. Then grab the trunk just below the lowest branch and gently sway it back and forth: The root mass should pivot with the trunk. 3. Then inspect the trunk of the tree (Fig. 10). It should be widest at the flare and then taper gradually to the top. A good taper represents a previous healthy growing regime, and provides stability to the tree. Any pruning cuts should be healing cleanly, and you should see no other visible damage. Myth 9: Young deciduous trees should look like miniature mature trees, with many spreading branches. Tree biology: A single main leader is a primary consideration for young deciduous trees. The branches should be well spaced up and down and around the trunk, appearing open and airy rather than dense (Fig. 11). Small branches closely spaced on the trunk eventually get thick and can become tightly spaced and weak (Fig. 12) as the tree matures. Tree biology: Evergreen trees should look like miniature mature trees. Myth 10: Plant large trees for quick establishment and a ?EUR??,,??mature landscape look.?EUR??,,?? Tree biology: Smaller trees transplant more easily and more successfully than larger diameter tree. They are easier to handle, less likely to be dropped or damaged in transit, and more likely to have adequate roots to support their crown. These smaller trees will often catch up to and outgrow larger caliper trees planted at the same time. Transplanting Guidelines Most people discount the importance of the process and techniques of transplanting trees. And, unfortunately, there are hundreds of books with information and diagrams that are incorrect, outdated and contrary to recent recommendations. Using these old procedures will eventually cause direct damage to the tree, or jeopardize the health of the tree. Myth 11: Tree trunks need to be deep in the ground. Tree biology: Tree bark needs to be exposed to air, light and dryness to remain healthy. The most common error made when transplanting trees is that they are planted too deep into the ground. A visible trunk flare is the proper identifying level for the transplant depth of all trees. Trunk flares of field-grown trees may be covered by soil during production operations at nurseries. If the trunk flare is not visible at the surface of the ball, be sure to excavate the soil to find the trunk flare before transplanting. The main reason trees are planted too deep is that the planting hole was made too deep by mistake. This is a particularly common occurrence with holes dug by backhoes because they frequently are not too accurate. If a tree is planted too deeply you may be able to see space around the trunk where it has ?EUR??,,??wiggled?EUR??,,?? in the breeze (Fig 13). If this is the case, the tree needs to be replanted to the proper depth. Myth 12: Burlap will deteriorate under ground and not damage roots. Tree biology: Contrary to popular belief, the burlap may not dissolve below ground. For this reason, the burlap and twine material should be completely removed. Specification: Some larger B&B trees will come supported by a wire basket. The burlap and basket should be removed at least one-third below the surface to allow new roots to grow unobstructed. Myth 13: All trees need to be staked. Tree biology: This is true if winds are strong, or for evergreen trees, or for large bare-root trees. But staking is not usually needed on deciduous trees harvested with the proper size root ball. These will remain upright if transplanted properly. Specification: If you believe stakes are needed, the stakes should be placed well outside the existing root mass, or driven into undisturbed soil below the planting hole. Myth 14: Guy wires must be tight. Tree biology: Trees need to sway to develop strong root support. If staking is needed, the holding straps and guys should be fastened loosely to let the trunk sway in the wind as it would naturally. This will let the roots develop strength needed to support the weight of the tree against wind throw after the stakes are removed. Myth 15: Stakes and guys are healthy for trees. Tree biology: Staking can seriously damage trees if not removed. Many contractors will not return to the site after the growing season to remove the stakes and guy wires. Specification: Many contracts have a one-season survival guarantee clause, and final payment may be delayed until then. Contracts should also specify that ties, guy wires and stakes be removed before final payment will be made. Myth 16: Water is needed for only two or three months after transplanting. Tree biology: Actually, irrigation may be needed for as long as 3 years after transplanting. This amount of time is not the usual concern of most landscape contractors, but you should inspect the condition of the root zone regularly and irrigate when needed if you want the tree to survive. Large caliper (3 to 4 inches) trees or trees planted in northern latitudes may need even longer attention. Root zone moisture is the primary factor in the survival and establishment of transplanted trees. The tree root mass should be moistened before removing the container or the burlap. Then the entire root zone should be thoroughly tamped and watered at transplanting to settle the soil around the root mass. Thereafter the original root mass needs adequate moisture levels to supply the leaves and stems for turgor (rigidity). Bad Planting Techniques Many typical planting specifications have errors. The trunk flares may be shown slightly below soil grade, and the planting hole may be deeper than the root ball, with loosened soil placed under the root masses. The loosened soil will not be able to support the weight of the tree and ball, thus the tree may settle to a point where the trunk flare is completely submerged. Narrow planting holes will be difficult to back fill and may contain air pockets, which will either stress the new root growth for water or allow the tree to settle into the space. The burlap may not be removed, but just folded back. These burlap layers will probably dry out and cause new roots to die when they try to penetrate the layers. If roots do survive, they will engulf the burlap and be weakened. Myth 17: Mulch volcanoes are good for trees. Tree biology: Mulch volcanoes (Fig. 14) will allow moisture and decay to affect the bark and may impair normal trunk development, or make the tree likely to become diseased. Girdling roots may develop around trunks of shallow-rooted trees, especially maples. Authors?EUR??,,?? Note: For more complete details on these topics, please log on to TLCforTrees.Info. Illustrations marked (NADF) are from the National Arbor Day Foundation Tree City USA Bulletins. Reference Watson, G. W. and Himelick, E. B. 1997. Principles and practice of planting trees and shrubs. International Society of Arboriculture, Champaign IL.