Changing of the Francis Quadrangle Arboreal Guard

The Francis Quadrangle, centrally anchored by the historic columns with Jesse Hall towering above, is probably the most iconic place on the University of Missouri campus. Many of the oldest buildings on campus, with their beautiful architecture and garden beds, surround the expansive manicured turf. It’s an idyllic setting, and easily the most commonly visited and photographed location in Columbia.

 

Encircling the quad is a walkway, generously shaded by twenty pin oaks (Quercus palustris), planted as saplings over 60 years ago. The legacy of that act lives on today, with the huge pin oaks shading the walkway and grass areas, perfectly framing the quad. Walking under these mature oaks inspires contemplation and gives a sense of time and gravity.

 

But these oaks are declining.

Pin Oaks

Pin oak is a Missouri native tree, and its territory stretches across much of the eastern U.S., predominately in low-lying, wetter areas and stream banks. Like most trees adapted to soggy conditions, pin oak has developed an affinity for not only moisture, but the more-acidic soils normally associated with these environments. Overall, the tree is tolerant and adaptable to a relatively wide range of conditions.

 

The species has been popular for decades among landscapers, homeowners, and nurseries. This is due to its very low propensity to maintain the initial seedling taproot, which results in a well-branched, fibrous root system, making it among the easiest oaks to successfully transplant.

 

In addition, it forms a stately shade tree, forming a symmetrical, moderately narrow, pyramidal shape that renders it both aesthetically pleasing and useful as an ornamental tree. It’s easy to see why pin oak continues to be the most commercially available and widely planted oak in the United States.

 

Certainly, planting these native trees was not a poor choice at the time. In fact, the trees performed admirably for decades, despite probably receiving less water, and more compaction from foot traffic, than they would prefer.

Increasingly challenging conditions

Years ago, in order to keep the turf bright and healthy, an irrigation system was installed. This has improved the turf’s usefulness and appearance tremendously, but unfortunately, has also gradually accelerated a slow-motion cascade of problems for the trees.

 

First, the installation itself certainly caused at least moderate root damage, since trenches had to be cut to lay hundreds of feet of pipe. The severing of many roots most likely weakened the trees slightly, although not irreparably. This damage could have been overcome within a few seasons. But as soon as the system was turned on for the first time, the root environment changed forever.

 

Roots that had grown and established over decades to seek water deep in the soil during dry summer months were suddenly saturated at those depths, starving them of the oxygen needed for respiration.

 

As mentioned, pin oaks tolerate persistent high levels of moisture, but a sudden, fundamental change to the established environment is difficult to overcome, especially for mature trees. Tree roots cannot move to higher ground; they rot, and must be replaced with new roots growing into the more favorable conditions. In this case, the trees’ entire root structures had developed over the years to withstand a very different, drier environment.

 

There is another, slower problem with irrigation water: calcium. The calcium carbonate found in hard water, and responsible for much of the “lime scale” in your home can have the same gradual effect on soil over time. Lime isn’t necessarily a problem in itself. In fact, liming soil is a common and accepted soil management practice in agriculture and turf management, but the purpose is always to reduce soil acidity, raising the soil pH balance.

 

Like many native trees, pin oaks are adaptable to a wide range of conditions. However, their need for soils that are at least somewhat acidic is non-negotiable, being physiologically locked-in with the roots’ ability to take up necessary iron. Iron plays essentially the same oxygen-exchanging role in plants as it does in humans: not very much is needed, but it is essential nonetheless.

 

Importantly, there is plenty of iron present in the soil to support the quad oaks. But when soil pH becomes too high, the tree cannot take in enough, and under the resulting iron deficit, chlorosis — leaf yellowing, especially of tissue between the leaf veins — begins to occur. As iron becomes less available, metabolism and growth will increasingly slow, and the plant weakens.

 

Indeed, these oaks now suffer compromised root systems on several fronts. And in their now-weakened state, they have become more vulnerable to other maladies, such as fungal problems. Branch die-back is increasing, posing a growing risk to those below, and requiring frequent, expensive trimming. Simple solutions to any one of the problems are either impractical or uneconomical in the long run, and many would themselves cause different problems requiring yet more solutions. Two trees have already been replaced with new pin oaks, which quickly began displaying symptoms of iron deficiency.

A solution

Unfortunately, the only truly long-term fix is to replace the pin oaks with something better adapted to the current conditions of the quad. Preliminary meetings are taking place to discuss possible replacements with a native species more adapted to the conditions on the quad. Another factor under consideration is utilizing two different species, perhaps alternated, to better protect against a single pest or problem affecting all trees at once. Then, if something happens in the future to one type, the quad remains half-populated with trees.

 

Whatever is decided, the final plan is not going to be easy, or cheaply implemented. A major hurdle is getting large equipment in and around the area, and dismantling the huge trees without destroying the columns, turf, buildings, or beds, and doing it quickly so as not to disrupt campus activities or require areas to be blocked to pedestrians during high-traffic school months. Replacement trees would be ordered early and grown for some time prior to the replacement, so they can be of at least moderate size when installed. The installation of replacement trees is expected to cost approximately as much as the removal.

Consider a legacy gift

If you are already a donor, or are considering donation, give some thought to the legacy that would be left by planting brand new rows of majestic trees lining the historic and beautiful Francis Quad, trees that will last for decades, providing beauty and shade for countless future visitors, faculty, staff, and students.

 

Plans being discussed may include commemorative plaques for tree “sponsors,” similar to the Carnahan Quad on the south side of Jesse Hall. Those trees (swamp white oak, Quercus bicolor ) are just beginning to come into their own now, about 15 years after planting, and have many decades still to come.

 

You can make a direct gift online or give us a call or email us more information on how to help ensure the lasting beauty of the Francis Quadrangle, the heart of Mizzou: 573-882-4240 or gardens@missouri.edu