Pleasant Hill’s tree canopy includes a typical mix for a central Iowa suburb: silver maple, green ash, oak, honeylocust, linden, and ornamental varieties planted in newer developments, along with whatever was already growing on lots that were developed from agricultural ground. Each comes with its own set of concerns at this point in the state’s tree health picture.

Emerald ash borer is the most urgent active threat facing ash trees in Polk County. EAB has been confirmed in all 99 Iowa counties, and Polk County is no exception. The beetle’s larvae tunnel through the inner bark, cutting off the vascular flow that moves water and nutrients through the tree, and the cumulative damage typically kills an infested tree within four years of infestation. For homeowners with healthy ash trees they want to keep, preventative insecticide treatment is most effective when started before visible decline sets in, with spring the optimal application window. For trees already showing significant canopy thinning or exit hole activity, removal is usually the more realistic path. Dead ash trees become brittle and structurally unpredictable quickly, which makes them more technically difficult and more dangerous to remove as time goes on.

Oak wilt is a fungal disease that spreads through Iowa’s oak population through two main pathways: root grafts between nearby oaks, and sap beetles attracted to fresh wounds during the growing season. Red oaks are significantly more susceptible and can decline and die within a single growing season once infected. White oaks are more resistant but not immune. We take this seriously on any oak pruning work, which is why we strongly prefer to do oak work during the dormant season when sap beetle activity is low.

Silver maple structural issues are a consistent concern in older sections of Pleasant Hill. Silver maples were planted widely across Iowa suburbs through the mid-20th century because they establish quickly and provide shade fast. The tradeoff is a tendency toward included bark, co-dominant stems, and interior decay at maturity, and many of the silver maples on Pleasant Hill’s older streets are now at or past the age where those issues become genuinely hazardous.

Honeylocust and linden are both common in Pleasant Hill’s newer developments and commercial plantings and are generally more structurally sound than silver maple, but honeylocust in particular develops significant deadwood in the interior of the canopy as it ages, which accumulates into a hazard if not addressed periodically.

Storm exposure. Pleasant Hill’s position in the eastern metro puts it directly in the path of storm systems that move through central Iowa from the northwest. The 2020 derecho caused widespread tree damage across the metro, and the pattern of storms coming through in subsequent years has continued to produce wind damage events. Trees with accumulated deadwood or structural defects are always more vulnerable during those events than trees that have been properly maintained.