Over the past few months I’ve come across two particular cases of declining crowns in White Oak. In both instances I was called out on site in order to diagnose what was causing the strain. Both oaks were mature specimens, perhaps in the age range of 60-80 years old. The signs of dieback had definite boarders, located on one particular half or in one specific quadrant of the crown. Through some questioning and historical forensics, I found that major site changes had taken place around both trees.

The first oak was located on a property boarder next to a golf course. The course was built sometime in the early 90’s. There was major grading on the course to manage surface runoff and shape the character of the course. That surface runoff now drains from the golf course directly onto the oak’s critical root system. Before it was a golf course, the neighboring property was an old farm. In fact, it is very possible that the oak tree in question was a property ‘marker’ of sorts, left to grow up along the stone wall as a natural property line marker. My client’s property, the parcel on which the tree sits, is also a newly constructed landscape and home. But, the homeowner had only recently noticed the issues of crown loss, albeit after some unseasonably wet years.

Upon inspecting the root flare, the perennials planted on top of the flare and crowding into the sinuses was the first clear issue. There was bark loss and some fruiting bodies of fungal activity present on the north and eastern side of the flare and lower trunk. There was also some frass present near soil grade where the bark loss was occurring above the sinus.

Looking up into the crown, I noticed the leaves of the tree had necrotic margins and interveinal necrosis with chlorotic halos. I had samples analyzed in the lab at Penn State for soil nutrient levels; as well as digital photos analyzed to determine the presence of bacterial leaf scorch. The foliar lab analysis came back without any alarming soil deficiencies, and it was noted that the necrosis on the leaves was not bacterial leaf scorch, but rather some other type of fungal infection.

I walked the property boarder with the homeowner, and he educated me on the microenvironment where the oak sits. He noted that in rainy weather, there is a significant amount of surface runoff that comes off the golf course property, runs over the critical root system of the oak tree and actually pools in his yard.

I noticed that the lawn area throughout the entire CRZ is manicured and mowed often. In wet conditions, a routine mowing program can easily lead to soil compaction in the CRZ.

The second white oak was located in the back yard of a property on which the home was built about twenty two years ago. During construction, there was major changes in grade to the west and southwest of the tree. A drainage swale was created that directs surface run off directly towards the root flare of the oak, and a drain tile was installed directly through the critical root zone of the tree on the southwest side. There was most likely severe compaction and root severance that took place during the excavation and construction process.

Also located on the southwest side of the tree where the major disturbance occurred with construction in the critical root zone, there were fruiting bodies present on the stem, starting at soil grade level and traveling up the trunk to a height of about six feet. There was also significant bark loss on this section of the stem where the fungus was colonized. Lower on the trunk, there were Armillaria rhizomorphs creeping out from under a piece of bark that was seperated from a necrotic area on a large buttress root. Along these necrotic margins though, was callus forming approximately two inches in width. It was somewhat reassuring to see active wood growth still occurring directly next to the presence of the shoestring fungus.

I had hypothesized that during construction when the root zone disturbance took place, major root loss occured with the installation of drainage swales and drainage tiles. Years later, this decay of major tree parts has finally materialized visually at the root flare and on the trunk in the form of cambium and bark loss, and in the upper crown of the tree in the form of crown loss. The signs of strain correspond directly to the area where construction was most invasive in the CRZ.

In both cases, historical forensics were required in order to piece together the puzzle of decline in these oak trees. Unseasonably wet conditions over the past few years have perhaps magnified the stress and strain of construction damage from many years ago. Perhaps there are still other clues yet to be found.

Mature trees have massive amounts of storage capacity in there large root systems, and in there expansive library of sapwood. But those storage assets can last only so long before the scale of stress and strain is tipped irriversably. But hope is not lost. There are mitigation options available.

For the first Oak tree, we removed the perennials around the root flare. Those plants were trapping moisture against the trunk and no doubt contributing in a major way to creating an environment condusive to the promotion of fungus and bacteria at such a critical junction of tree anatomy as the root flare. This will help to dry out this area, at least on the surface where the cambium can begin to create some callus and woundwood in the future. We also removed major deadwood in order to create a baseline for measuring further dieback in the future. Monitoring is a form of mitigation too, and so we will monitor this crown into the future and see what responses we see. Perhaps more high level treatments like soil aeration (to improve drainage) and sterilization of the fungal infections on the stem will be utilized on future visits. The conversation of other drainage mediation with the client had also been touched upon.

For the second oak tree, a recommendation was made to mitigate the surface runoff directed at the decaying areas of the stem and root system with soil aeration with the pneumatic air spade. Monitoring the development of the callus and woundwood along the necrotic margins on the trunk and buttress root will also be a part of the ongoing management of the tree. I suggested removing deadwood for risk and aesthetic purposes, but the client was not willing to pursue that prescription at the present time.

Wendell Berry writes that “what can’t be helped must be endured.” This sentiment seems fitting of mature trees that find themselves in such fractured environments. The flora, fungal networks and soils these Oaks grew up in have been fractured, compacted and waterlogged. The trees are subjected to drastic changes in their growing medium and in their symbiotic relationships to microbiota in the soil, shocking the physiology on which they built solid foundations in a fitting environment. Drainage patterns surrounding the trees have created soupy conditions on sites that were previously drier, rocky farmland and forest. For all intents and purposes, over the past twenty years, these trees have been living in different worlds than those in which they resided in the first half of their life. Added to that is the recent onset of unseasonably wet years, combined with humid conditions which breed fungal pathogens that further require massive storage assets to combat, adding even more stress to a system that is nearly maxed out. It is shocking, and even a marvel, that these trees still stand up bravely to such vast and brutal changes. They reach out, skyward and in the wet subterranean soil, searching for the community that they were once a part of. Perhaps they find small bits and pieces. And those tiny treasures are, for now, enough to endure.