Tree Death in the Landscape

Avoid tree death in garden and urban landscapes by using appropriate planting and cultural techniques, good sense and attention to detail, especially during construction.

Tree death in the landscape sounds grim, doesn't it? Tree death changes your design and tree removal is expensive. However, by using reliable arboriculture information, ornamental trees in garden and urban settings can live long and healthy lives.

Improper landscaping and construction around established trees is a widespread problem, according to arborists. Badly damaged or cared for trees appear healthy for a year or two after a project but gradually deteriorate and die. The culprit in tree death, in many cases, remains a mystery because of the time span between the initial construction damage and death.

Disrespect for tree growth and physiology, and their interactions, most likely resulted in these fatal examples:

• Tree roots may extend three times the width of branches. The primary feeder roots are usually in the upper twelve inches of soil. Sugar maple (Acer saccharum) trees lined the main approach to a small New England town before the necessity of extensive utility lines. One suggestion was to bury wires underground because residents did not want utility poles and lines mixed with their beloved tree canopies. Town meeting statements presented by arborists about consequences of root damage convinced town officials to run lines above ground instead of burying them. The result is still death for these centuries-old trees because of ripped roots during pole installation. However, death has been slower.
• Bark wounds on tree trunks and large branches cause infections and infestations which cause trees to die well before their life expectancy. Equipment bouncing off young trees during septic tank installation left slashes down to living wood in young trees. Rather than just cut these trees down, the contractor covered the slashes with black paint. This paint may keep pathogens out of the tree, but the long-term prognosis is not good.
• Wells or landscape depressions around tree trunks are worthless without properly installed networks of perforated tile to drain water and bring oxygen to tree roots.
• Layers of soil added over root systems can kill a large tree within three years by suffocating tree roots. Three Norway maples (Acer platanoides) graced a concrete gathering place on the north side of a community center. Surprisingly, they persisted for almost two decades, but their yearly demise was visibly apparent. These trees battled two problems:
  • Planting site for each was a four-foot-square patch of soil integrated into the concrete decking with no irrigation or drainage systems; and
  • Each spring, grit, sand and salt from winter snow and ice removal remained on soil covering the roots.
• Soil compaction by heavy equipment use, car and truck parking or heavy foot traffic over tree root zones can bring speedy death to mature trees. Vehicle and foot traffic are harmful to venerable trees gracing small town commons and squares, but are not always seen as a problem. Citizens want and psychologically need to utilize the comfy space under these trees; restricted areas over roots are either nonexistent, too small or ignored. A Draconian but effective measure is one used by large public gardens such as Longwood Gardens in Kennett Square, PA. Foot traffic is prohibited over the root areas of certain admired and revered trees such as giant sequoia (Sequoiadendron giganteum), dawn redwood (Metasequoia glyptostroboides), incense cedar (Calocedrus decurrens), and Atlas cedar (Cedrus atlantica).
• Grade changes, even well away from trees, may alter water levels and reduce tree life expectancy. I sit and look out windows while visiting in my daughter's home in Charlottesville, VA and see several dead trees. I contemplate the expense of tree removal. She and her husband are not the first owners, but they are the current owners. Though the house is less than a decade old and the wooded area is more than 50-feet away from the house, tree death from construction mistakes is just becoming noticeable. Most of the tree fatalities are probably due to grade changes, but without doubt the other construction errors in the landscape mentioned above played a part.

The International Society of Arboriculture (ISA) created the Trees are Good brochures to educate homeowners and the public about quality tree care. Here are two titles I believe are particularly important:

• Avoiding Tree Damage During Construction
and
• Treatment of Trees Damaged During Construction.

©

Text and photograph by Georgene A. Bramlage, August 30, 2006. Reproduction without permission prohibited

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