It is a large shrubortree[8] growing to 22 metres (72 feet) tall, although where it is common in the low-elevation Sierra Nevada foothills it seldom exceeds 10 m (33 ft). The dark-green leaves—appearing grayish from a distance—are usually small, 2–5 centimetres (1–2 inches) long, thick, and often spiny-toothed at higher elevations, particularly on young trees. The male flowers are on catkins, the female flowers in leaf axils. The acorns are 1–2 cm (1⁄2–1 in) long, and mature the second season (about 18 months) after flowering.[8]
Although originally published by Alphonse Pyramus de Candolle as "wislizeni",[2] some sources, e.g., Jensen in Flora of North America,[8] mistakenly spelled the specific epithet "wislizenii." Correct spelling is with one "i," per ICN article 60C.2.[9] Wislizenus' specimen was thought by de Candolle to have been collected in Chihuahua, Mexico. However, German-born American botanist Georg Engelmann later corrected the location to the American fork of the Sacramento River near Auburn, California.
California physician and botanist (and one of the founding fathers of the California Academy of Sciences) Albert Kellogg described an oak in an 1855 publication as Quercus arcoglandis (spur acorn oak),[10] apparently the same species as Q. wislizeni. This clearly predates French-Swiss botanist de Candolle's 1864 name, and if confirmed to be this same taxon would have priority. More investigation is needed to resolve this taxonomic conflict.
Currently there are two recognized varieties of interior live oak:[11]
Q. wislizeni A. DC. var. wislizeni (1864)
Q. wislizeni A. DC. var. frutescens Engelm (1878).[12] This is an invalid taxon. Engelmann's Q. wislizeni var. frutescens description is virtually identical to de Candolle's Q. wislizeni, while Engelmann's Q. wislizeni description most closely matches Kellogg's Q. morehus.[13]
The interior live oak is a red oak (section Lobatae) in the California Floristic Province (series Agrifoliae). Q. wislizeni hybridizes with California black oak(Q. kelloggii) (= Quercus × morehus, Abram's oak). All California red oaks show evidence of introgression and/or hybridization with one another.
A common alliant tree is gray pine (Pinus sabiniana).[13]
^ abde Candolle, Alphonse Pyramus (1864). Q. wislizeni (in Latin). Vol. 16. p. 67. {{cite encyclopedia}}: |periodical= ignored (help)
^"Quercus wislizeni A.DC". IPNI. Retrieved August 29, 2010. "Description of Q. wislizeni was published in Prodromus Systematis Naturalis Regni Vegetabilis ... (DC.) 16(2.1): 67 (1864)."[2]
^J. McMeill et al. (eds). 2012. International Code of Nomenclature for algae, fungi, and plants. Regnum Vegetabile 154. Koeltz Scientific Books. ISBN978-3-87429-425-6
