Summertime in Riparian Buffers: Maintenance Items to Consider

Summertime is often busy and typically filled with people unplugging from their normal schedules for vacations, parties, outdoor work, festivals, and many other, often fun, things. One activity we often push aside in summertime is riparian buffer maintenance. Buffer maintenance goes well beyond replanting trees and therefore goes beyond the spring and fall seasons. Members of Penn State Extension's Water Resources Team, the Agriculture and Environment Center, and the Center for Agricultural Conservation Assistance Training recently teamed up for some riparian buffer maintenance and replanting for two of our buffers. One of the buffers is along Spring Creek in Dauphin County, and the other is at the Southeastern Agricultural Research and Extension Center (SEAREC) in Landisville, PA. These maintenance days were huge learning days for the team. Here are some of the lessons we learned.

Tree Mortality Rates Are Best Determined in Early Summer

Springtime is usually when people in charge of maintaining buffers check to see if a tree is dead or alive. The buds are present and often budding. There are few weeds in tree tubes that can be mistaken for green tree vegetative growth, and let’s face it, we are out there standing up tree tubes, so might as well see if a newly planted tree survived the winter. We did this exact thing for our buffer in Dauphin County. In fact, this buffer is part of a long-term research project where we track the growth and mortality of newly planted trees. Each tree in this buffer has been heavily studied and tracked since 2021.

Part of this study is to record whether a tree is dead or alive so that we can keep up with replanting when necessary. On May 1^st, 2025, a group went out to update the tree mortality records of this buffer for this year's replanting. Each tree was thoroughly inspected and recorded in our electronic notes via the ArcGIS Survey123 tablet tool. This data was brought back to the office, and tree species were purchased based on the results. Now for the interesting part. When the whole group went out to do more buffer maintenance and replant the buffer on June 11^th, 2025, roughly 25% of the trees that were thought to be dead at the beginning of May were now considered alive. Many of these trees had late buds that were not obvious in May but were leafing out in the middle of June (Figure 2). These trees had bounced back after getting injured and were either stump sprouting or growing new buds on their original trunk. If we had waited until early summer to assess tree mortality, we could have more accurately determined the number of each species that needed to be replanted. A suggestion for the future is to determine buffer tree mortality in early summer and replant any dead trees in fall or the following spring.

Summer Flooding Can Help Determine an Area's Tree Species Suitability

One of the major guidelines for planting trees is to find a suitable spot based on a tree species’ needs. Site factors include sun availability, soil pH, distance to infrastructure including powerlines, and perhaps the most important variable in riparian areas: soil wetness and frequency of flooding. When thinking about flooding, typically we think of springtime floods. These floods are the most common as soils are either frozen or saturated due to lack of vegetation, and additional rain causes runoff and flooding. However, summer floods can prove even more beneficial for determining where to plant certain tree species. These floods are often less common and can really indicate the easily flooded areas and the soil areas that hold water for greater periods of time.

The recent heavy rain events in central Pennsylvania this summer have caused flooding on our buffers, especially the riparian buffer at SEAREC. Figure 3 shows the most recent flood right before our buffer maintenance day. This flood was widespread throughout the buffer and really indicated that the entire length of the buffer should have trees that can survive in wet conditions for extended periods of time. Large, localized rain events are expected to increase in frequency, making this type of summer flooding more common and the species selection of trees incredibly important.

Summer Flooding Can Cause Holes to Form Near Tree Shelters

Perhaps the most common buffer maintenance item thought of after flooding is bent tree tubes and stakes. While this does frequently happen and needs to be corrected, another item to look for is the formation of holes next to tree tubes. Figure 4 shows a hole just to the right of the tree tube, formed from the soil being saturated and then eroded by the stream. If these holes are not filled in with soil, they can cause damage to the tree’s roots as well as tree mortality if root damage is severe. Roots need to be in soil to survive. Exposing them to air for long periods of time can cause root death, and this can cause tree death, especially in younger, recently planted trees. Additionally, this hole in the ground next to the tree can lead to damage by rodents and other burrowing animals. Thankfully, the fix is easy. A scoop of soil from an area near the tree is often all that is needed to fill in a hole. Doing this soon after a hole is formed can increase a tree's chances of surviving to the next growing season.

Summertime is a great time to unplug and head outside for lots of fun reasons. Hopefully one of these reasons will now be additional buffer maintenance, especially to see a tree is alive. Those small trees are very resilient and can often bounce back after being injured or damaged. So, let's get out there and enjoy that summer sunshine while checking on our riparian gardens!