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Decorah's Tree Board Surveys Street Trees and Plans for Future Plantings

Posted: Mon, Mar 20, 2017 1:46 PM

Volunteers working for the Decorah Tree Board have completed a survey of boulevard trees in most older neighborhoods of the city. More than 2,100 trees representing 79 species and hybrids were identified, measured, and evaluated as to condition.

Norway Maple was the single most abundant species with 18 percent of the total, followed by Sugar Maple and Green Ash at 13 and 12 percent respectively. Other common trees in order of abundance were the Freeman Maple, Flowering Crabapple, Silver Maple, Red Maple, Honey Locust, Black Walnut, Bur Oak and Hackberry.

Trees ranged in size from saplings of various species to a Silver Maple with a trunk diameter of 51 inches. Most of the common species had an average diameter of 18 inches or more, indicating a fairly mature population. The average size of all trees was 60 percent greater than in 1992, when Decorah's trees were last surveyed.

According to Peter Van Der Linden, who organized and led the survey, trees rated "poor" were either declining or exhibiting significant structural problems such as large cavities or cracks. Trees rated "fair" were for the most part healthy but had growth defects that might shorten their lives or make them more susceptible to storm damage. "Corrective pruning can prevent growth defects and should be conducted regularly during the life of a tree," he noted.

About one in seven of Decorah's street trees are ash and are likely to be killed by the Emerald Ash Borer, an insect pest accidentally introduced from Asia and now spreading in the city. "Once the ash trees are gone, more than half our remaining trees will be maples. Having such a large population of one type of tree leaves us extremely vulnerable to pests and diseases," Van Der Linden noted.

To enhance the health of our urban forest, the City of Decorah is working to increase the number and diversity of trees planted in the city. To make trees more affordable, the City provides vouchers that reduce the cost of the boulevard trees purchased from participating local garden centers. The Tree Board will also be planting trees along Montgomery Street this spring, thanks to a grant from Power of Trees, a community tree planting program offered by Black Hills Energy and Trees Forever.

Volunteers are welcome to participate in the planting which is scheduled for April 22nd, weather permitting.

For more information about the tree survey, the city voucher program or tree planting projects, contact City Forester Robin Sailor at 563-277-5153, or Street Superintendent Kevin Nelson at 563-382-2157,