On May 10, 2013, two of the four treewells that I plant in front of my building, each with a pin oak in the center, looking good.
On Sept. 26, the same two treewells.
The far one looks great, the other, pitiful. Both watered by building staff, both with the same with the same annuals planted lovingly by me in spring. What happened?
Other Ellen and I did an analysis. Our pet theories coincided with slight variations.
It all comes down to water. The Great one above, is right in front of the building entrance, with a tree planted just 2 years ago, shallower roots but more soil. The soil was replaced at the time of tree-planting, less dog pee. The soil level is three inches below the concrete rim, so the treewell retains the water until it percolates downward.
The Pitiful one is closer to the corner where the wind whips through, drying out the leaves. In the center lives a tree planted 16 years ago, in a smaller plot; established tree roots are everywhere. Since it is further from the doorman, we surmise that more dog owners allow their dogs to pee there. But probably most important, the tree roots have heaved upward, pushing the soil level to the top of the concrete barrier. If the guy watering tries to finish quickly with a heavy flow both water and soil flood over the rim, making a big mess. He stops before this happens.
Not enough water goes to the annuals!!!!!!!!!!