Centenary College Arboretum: Tree of the Week: Bur Oak (Quercus macrocarpa)

Thursday, September 14, 2017

Tree of the Week: Bur Oak (Quercus macrocarpa)

The autumnal equinox is next week, marking an end to summer. The cooler weather over the past week has signaled the coming change in seasons. With plenty of cloud coverage and a nice breeze, we haven't been desperate for shade. So, with the end of summer so goes too our discussion of shade trees. The last entry for 2017 in this series is the bur oak (Quercus macrocarpa).

There are two bur oaks in the arboretum collection. Both are over twenty years old and both provide a good amount of shade on the eastern clay slope of the arboretum. The images below are from the older of the two trees. This bur oak was purchased from Home Depot and planted in October 1993. It is of interest this week because of its curiously large acorns. It's hard to say if the cap of the acorn more closely resembles the Scottish tam, the Russian ushanka (ear-flaps tied up), or the Caucasian papakha.

All photos below were taken shortly before noon on a mostly cloudy day.

The bur oak is pictured above in the foreground, with a Shumard oak (Quercus shumardii) directly behind it. The Shumard is a few years older and has an obviously thicker trunk. The two compete for sunlight on this eastern clay slope, shading the gravel path during the heat of the day.

The bur oak is pictured front and center, with a long-leaf pine (Pinus palustris) and French mulberry bushes (Callicarpa americana) closer to the brick wall.

Approximately 25 years-old, this bur oak is already providing a good amount of shade.

The underside of the lobed leaf (quite large) is light green and hairy to the touch.

The branches of the bur oak have corky ridges similar to those seen on the bark of the winged elm (Ulmus alata) and the sweetgum tree (Liquidambar styraciflua).