Gardening Help FAQs

Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

What should I do to my trees that were damaged during construction?

Construction activity damages or destroys many healthy, mature trees each year. Contractors often remove valuable trees rather than preserving them through proper planning. But more often, trees are left in place where they are seriously damaged. The damage is mostly unintentional. Caused by neglect resulting from lack of knowledge about what is required to preserve trees and keep them healthy through the drastic changes that occur in the tree's root environment during and after construction. Ultimately, construction activity kills many trees although problems may not become obvious for several years after construction.

Trees may suffer a variety of injuries during construction. Most obvious are the broken branches and the gouges, gashes and tears in trunks and branches. These injuries often go untreated, are typically slow to heal and may result in large columns of decay in the wood behind the wound. Root damage may also occur resulting from the installation of building foundations close to trees.

More subtle damage injures tree root systems, too. Heavy equipment seriously compacts the soil by continually passing over tree's root system during construction. The compaction is usually long term and may affect the movement of water and air into the tree's root system for years to come. Builders often pile up soil and construction materials over root systems for extended periods of time during construction. This physically damages roots and reduces air and water movement. Other damage occurs when soil is scraped off the surface. Because most roots, even on mature trees, are in the top foot of the soil, the scraping injures or destroys these roots. Fill is often used on construction sites. Putting fill soil over tree roots limits the amount of air and water that reaches the roots. In addition, the quality of fill soil is usually poor. It often has a high clay content and compacts very easily. Dumping poor fill soil over already damaged roots makes it that much more difficult for water and air to penetrate to tree roots. Construction activity often changes the slope or grade of the soil. This can alter surface water drainage and potentially make a drier or wetter root environment for trees. Most trees, especially mature trees, are unable to adapt to these changes.

Unless contractors take proper steps, construction radically changes the soil. This change is what causes the slow decline and death in many trees in newer subdivisions and other newly developed areas. During the decline, the main branches usually die back. Although construction injures all trees to some degree, certain trees suffer more. White oak, sugar maple and American beech are very intolerant of soil disturbance and are most often injured during construction activity. If you plan to build on a wooded lot, take steps before and during construction to preserve the most valuable trees. A consulting arborist can help develop a plan and are listed under "tree service" in the yellow pages.

We recommend this excellent Iowa State University publication: Preventing construction damage to trees for more information and line drawings.