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5-2011 White Oak Part of Global Oak Presence W. John Hayden University of Richmond, [email protected]

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Recommended Citation Hayden, W. John. "White Oak Part of Global Oak Presence." Bulletin of the Virginia Native Plant Society 30, no. 2 (May 2011): 3, 8.

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Bulletin of the Virginia Native Plant Society White oak part of global oak presence As we act locally celebrating mal names depends on numerous de- black oaks is well to our south! white oak, Quercus alba, as the 2011 tails: the degree of lumping or split- Leaves may be deciduous or ever- VNPS Wildflower of the Year, it is ting among subgroups, for one thing, green, lobed, toothed, or entire; perhaps appropriate to think glo- and the rank in the taxonomic hier- toothed leaves have prominent bally for a few moments and con- archy— subgenus, section, or subsec- bristletips; acorns take two years sider the breadth of diversity encom- tion—to which any subgroup is as- to reach maturity for most species. passed by the oaks. Quercus is a big signed, for another. Different bota- Included here are familiar trees genus, easily the largest in its fam- nists see these things differently and, like the red, scarlet, pin, black, ily, the Fagaceae. Approximately 400 accordingly, they wedge oak natural blackjack, willow, water, turkey species of oak are oaks, and a plethora of trees from known, and they are high-altitude regions of Mexico widely distributed in Quercus alba and Central America. the northern hemi- white oak White oaks (Quercus, sphere. We tend to Illustration by Lepidobalanus, Leucobalanus, think of oaks as tem- Nicky Staunton Mesobalanus): Species belonging perate zone trees, but in to the white oak group occur both the New World, their in the New and Old Worlds; it is range extends south thus geographically the most wide- through the mountains spread subgroup of oaks. Some 200 of Central America to species have been recognized, with Colombia and in the 51 found across the breadth of Old World, into the tropics of south- diversity into the categories of clas- North America north of Mexico. east Asia. sification to fit their particular inter- Leaves may be deciduous or ever- As might be expected of such a large pretation. Consequently, we still see green, lobed, toothed, or entire; when and widespread genus, several sub- some proliferation of oak subgroup present, leaf teeth are never bristle- groups of oaks can be recognized. Oak names. For the discussion that fol- tipped; acorns mature within a single subgroups were first distinguished on lows, names will be used in a strictly season. The white oak group includes the basis of morphological features; in informal fashion independent of many familiar local species includ- recent years molecular (DNA) charac- taxonomic rank, with an attempt to ing white, burr, post, chestnut, and ters and the details of pollen structure include frequently used synonymous swamp chestnut oaks. The evergreen have reinforced the definition of these (or nearly synonymous) alternative live oaks (Quercus virginiana and groups. Specialists do quibble about the group names. close relatives) of the southeast and details, but recognition of six prominent Intermediate or golden-cup oaks Gulf coast also belong here, as do subgroups seems well established in (Protobalanus): Protobalanus consti- many more species from Mexico, recent literature. Yes, six! Only two of tutes the smallest subgeneric group of Central America, Europe, and Asia. these subgroups are found in eastern oaks, consisting of just five species Quercus robur, the English white North America. It is remarkable how that range from southern Oregon to oak, is perhaps the best-known ex- many of the references for oaks in our northern Mexico. Leaves are entire or otic species of this group; it and region refer to our two local subgroups toothed and evergreen, acorns take some of its hybrids are sometimes as if they were the only subgroups of two seasons to reach maturity, and cultivated as specimen trees in the oak. In truth, the many oaks that grace acorn caps are densely glandular U.S. Also notable is the gall or our woods represent just a fraction of hairy, so much so that the individual dyer’s oak, Quercus lusitanica, oak diversity on a global scale—hence bracts are indistinct except for their from the Iberian Peninsula and the motivation for outlining this broader tips. Quercus chrysolepis (canyon live nearby northwest Africa; insect-in- perspective of the genus. Two of the six oak, maul oak), a highly variable spe- duced galls that form on this (and major groups of oaks occur only in the cies, is the most widespread member some related species) yield tannins New World, three are restricted to the of the group. used as a dark-colored dyestuff. Old World, and one, the white-oak Red/black oaks (Lobatae, Cycle-cup oaks (Cyclobalanopsis): group, is found in both. Erythrobalanus): The red/black Cycle-cup oaks encompass about 150 While the composition of oak sub- oak group is also restricted to the species found in tropical and sub- groups seems to be nearing consen- New World, with some 195 species, tropical regions of southeast Asia. sus among botanists, the subgroups' only 35 of which occur north of These evergreen oaks have remark- nomenclature remains chaotic. Suf- Mexico—which means that the true ably distinctive acorn caps that consist fice it to say that application of for- center of diversity of “our” red/ (See Oak diversity, page 8) May 2011 Page 3 Bulletin of the Virginia Native Plant Society •Oak diversity (Continued from page 3) Cork oaks, incidentally, make pro- is a remarkable genus indeed that of a series of ringlike ridges. Whereas digious quantities of outer bark, stoppers the bottle of wine that we our familiar acorn caps look scaly, i.e., cork, an adaptation by which sip while dining on truffles that grow cycle-cup acorn caps look as if they the trees are insulated from sporadic upon its roots and also furnishes the have been turned on a lathe. In some fires that sweep through this spe- table and chair from which we enjoy species the acorns are borne in re- cies’ natural habitat. these sublime refreshments. markably dense clusters. Quercus Holm or holly oak & relatives W. John Hayden, VNPS Botany Chair myrsinifolia, the Chinese evergreen (Ilex): The holly oaks are also strictly oak, is rarely cultivated in our region, Eurasian, sometimes included within but several specimens are visible the cerris oak group, but distinguish- from my office window on the Uni- able by details of pollen structure. versity of Richmond campus. Some- Holly oak, Quercus ilex, is so named times the cycle-cup oaks are split out because its spiny leaves resemble as a separate genus. those of holly; in fact, some sources Cerris oaks (Cerris): As a group, indicate that ilex is the classical Latin cerris oaks are strictly Eurasian. The name for this oak, which only later leaves are evergreen or deciduous, came to be applied as the genus name bear bristle-tipped lobes, and the for hollies. Quercus ilex is also no- acorns mature in two seasons. A few table as one of several oaks that sup- species from this group are sparingly ports the growth of truffles. Another cultivated in the U.S., most promi- interesting species from this group is nently, Quercus acutissima, the Q. coccifera, the kermes oak; this tree sawtooth oak, and less frequently, Q. is host to the kermes scale insect, cerris, the European Turkey (or Turk- which can be harvested and pro- ish) oak. Quercus suber, from which cessed to yield the natural red dye cork is harvested commercially in called crimson. southwestern Europe and north- That’s just a brief overview of oak western Africa, also belongs here. diversity. When you think about it, it