Is Quercus rugosa Showing Its Roots?

We know that some oaks, particularly Quercus robur, can produce forms with unusually cut leaves. Many of these have been documented in International Oaks and are listed at oaknames.org. We were very surprised, however, to find a very unusual shoot on a tree of Q. rugosa at the Puebla University Botanic Garden in Mexico.

This species normally has unlobed but distinctly toothed leaves, but a single shoot was recently found with leaves deeply lobed. It seems to be unstable as later growth produced normal leaves, but we will certainly be keeping an eye on it. What is happening here is not clear. It could be a simple mutation, but as we know that the Mexican oaks, which most often have unlobed or shallowly lobed leaves, derive from ancestors further north where deep lobing is more common, is this tree expressing an ancient and long-hidden gene? What it does seem to show is that the genetic difference between lobed and unlobed leaves in oaks, often an important identification feature, may be very small. The tree is about 25 years old and was grown from seed collected on Cerro El Pinal in Puebla.

Allen J. Coombes and Maricela Rodriguez

Photos © Allen J. Coombes