Agenda - Environmental Policy Board - 11/02/2009

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Step #8: Adapt Maintenance The pruning of boulevard trees can be very time consuming if the trees receive the kind of work that is necessary to increase their longevity. For example, pruning for proper branch structure and apical dominance helps a tree to withstand ice and storm damage. However, this may not be the best use of resources for a tree species that will not be around for the long term future. Recognizing that the arrival of EAB is just a matter of time, Forestry Division crews are spending less time pruning ash trees that other types. Ash tree pruning now consists of two basic steps. These are the removal of low limbs that interfere with pedestrian and vehicle traffic as well as the removal of deadwood. The time saved pruning ash trees can be spent on longer lasting species. Ironically, one of these is the disease resistant elms that show promise in tough urban settings. Step #9: Stop Planting Ash The loss of thousands of elm trees to DED in the late 1970s caused a need for inexpensive yet fast growing trees that could endure tough city conditions. This resulted in the unintentional over planting of ash trees by home owners and municipalities. Unlike many cities and villages, Minneapolis adopted a Master Street Tree Planting Plan (MSTPP) in the early 1980s. This helped ensure species diversity and limited the number of ash planted on public properties. Over time the MSTPP developed into a dynamic document. Species that were prescribed in the 1980s proved unsuitable over the next twenty years. Even when following the MSTPP, the number of ash on boulevards and in parks increased. It was not uncommon for the MPRB to plant over 300 ash each year. With the realization of EAB's destructive nature, the Forestry Division reduced the number of ash planted to 44 in 2005 and 9 in 2006. Since 2007, no ash trees have been planted by the MPRB. Step #10: Replacement The perfect scenario for any urban forest would be one in which there were no disease or insect pest to deal with. However, even in this ideal setting there would still be a need to remove aging trees and replace them with new ones. This is because much of an urban forest is manmade. Without replanting, the urban forest would suffer from senescence and eventually die off. One of the goals in the battle against EAB is to slow the insect's arrival to Minnesota for as long as possible. During that time, there are ash trees that will reach the end of their life cycle and need to be replaced. The MPRB Forestry Division will use this opportunity to replace ash with other species. Other opportunities for ash replacement will also be pursued. These include situations where ash was probably not the best choice at the time of planting. 5