Excerpts from Jim Conrad's
notes appended to the April 12, 2015 Newsletter describing a visit to San Juan de Monte Ecological Reserve on the south side of Las Vigas, on the northern slope of Cofre de Perote Volcano, at about 8100ft (2500m) in elevation, Veracruz state, MÉXICO
NET-LEAF WHITE OAK
About an hour's hike southward from Las Vigas, thus upslope toward Cofre de Perote Volcano well south of town, and hidden by forested foothills, I camped at the edge of a piney forest developed on thin soil of black basalt rock. The pines are all the same height, maybe 30 years old. On a rocky cliff overlookingf a shallow, steep-walled valley, some youngish oaks maybe 15ft tall (5m) appeared. You can see their leathery, round-tipped, broadly-eared based leaves with very hairy undersurfaces and shiny, dark green surfaces below:
In that picture you can see that the tree's trunk is dark gray, badly split, and too young to be showing flakes or ridges. I looked in vain for acorns below the tree, but I did notice some female flowers -- future acorns -- with well exposed, Y-shaped stigmas with curling arms, shown below:
The Flora of Veracruz doesn't have its oak section finished yet, but I had reason to hope I could identify this species, since I recall seeing it in highland oak forests of other parts of Mexico. The big, unlobed leaves with broad ears or lobes at their bases and densely covered with matted hairs are fairly distinctive.
Still, it was a challenge, especially because the species I think it is, is very variable. Luckily, in found a few isolated canyons in western Texas, near the Mexican border, so the species is described in the Flora of North America.
Best I can tell, this is QUERCUS POLYMORPHA, which the Flora of North America calls the Net-leaf White Oak. Other English names for it include Mexican White Oak, Monterrey Oak, and Netleaf White Oak The Flora describes it as occupying many habitats, from riversides to margins of thorn scrub, to oak-pine woodlands and cloud forests from thoset populations in Texas south throughout Mexico into Guatemala.
If you do an image search on Quercus polymorpha, you'll find pictures of quite a variety of leaf shapes. Leaves on Quercus polymorpha trees are much more slender than ours, and bear broad teeth. Among the more constant leaf features are the leaves' leathery texture, the manner by which the blade margins curve downward a little, and the leaves' dense hairiness.
In hot, arid Texas where oak blight is killing many native oaks, Quercus polymorpha is showing signs of being able to survive the blight, and may have a future as an important ornamental tree there.