Quercus virginiana, also known as the southern live oak, is a normally evergreen oak tree native to the southeastern United States. Though many other species are loosely called live oak, the southern live oak is particularly iconic of the Old South.
A large number of common names are used for this tree, including "Virginia live oak", "bay live oak", "scrub live oak", "plateau oak", "plateau live oak", "escarpment live oak", and (in Spanish) "encino". It is also often just called "live oak" within its native area, but the full name "southern live oak" helps to distinguish it from other live oaks, a general term for any evergreen species of oak.
This profusion of common names partly reflects an ongoing controversy about the classification of various live oaks, in particular its near relatives among the white oaks (Quercus subgenus Quercus, section Quercus). Some authors recognize as distinct species the forms others consider to be varieties of Quercus virginiana. Notably, the following two taxa, treated as species in the Flora of North America, are treated as varieties of southern live oak by the United States Forest Service: the Texas live oak, Quercus fusiformis (Q. virginiana var. fusiformis) and the sand live oak, Quercus geminata (Q. virginiana var. geminata).
Matters are further complicated by southern live oaks hybridizing with both the above two species, and also with dwarf live oak (Q. minima), swamp white oak (Q. bicolor), Durand oak (Q. durandii), overcup oak (Q. lyrata), bur oak (Q. macrocarpa), and post oak (Q. stellata).
Typical southern live oaks are endemic from southeast Virginia to Florida, including the Florida Keys, and west to southeast Texas. Texas live oaks grow primarily in Texas, on the Edwards Plateau and the Rio Grande Plain, but can be found as far west as Terrell County, Texas, in southwestern Oklahoma and northeastern Mexico. Sand live oaks grow from North Carolina to Florida in the east and Mississippi in the west.
Although typically evergreen, the leaves persisting until the time growth resumes in spring, a live oak's defoliation may occur sooner in marginal climates or in dry or cold winters.
The bark is dark, thick, and furrowed longitudinally. The leaves are stiff and leathery, with the tops shiny dark green and the bottoms pale gray and very tightly tomentose, simple and typically flattish with bony-opaque margins, with a length of .75 - 6 inches (2 – 15 cm) and a width of .4 - 2 inches (1 – 5 cm), borne alternately. The male flowers are green hanging catkins with lengths of 3 - 4 inches (7.5 –10 cm). The acorns are small, .4 - 1 inch (1 - 2.5 cm), oblong in shape (ovoid or oblong-ellipsoid), shiny and tan-brown to nearly black, often black at the tips, and borne singly or in clusters.
Depending on the growing conditions, live oaks vary from the shrubby to large and spreading: typical open-grown trees reach 15 meters (45 feet) in height, but may span nearly 50 meters. Their lower limbs often sweep down towards the ground before curving up again. They can grow at severe angles, and Native Americans used to bend saplings over so that they would grow at extreme angles, to serve as trail markers.
The southern live oak has a deep tap-root that anchors it when young and eventually develops into an extensive and widespread root system. This, along with its low center of gravity and other factors, makes the southern live oak extremely resistant to strong sustained winds, such as those seen in hurricanes.
The southern live oak grows in a wide variety of sites but is not fire-tolerant and occurs most any place free from fire that is not too wet. They can withstand occasional floods and hurricanes, and are resistant to salt spray and moderate soil salinity. They tend to survive fire, because often a fire will not reach their crowns. Even if a tree is burned, its crowns and roots usually survive the fire and sprout vigorously. Furthermore, live oak forests discourage entry of fire from adjacent communities because they provide dense cover that discourages the growth of a flammable understory. Although they grow best in well-drained sandy soils and loams, they will also grow in clay. Live oaks are also surprisingly hardy. Those of southern provenance can easily be grown in USDA zone 7 and the Texas live oak (Quercus virginiana var. fusiformis), having the same evergreen foliage as the southern variety, can be grown with success in areas as cold as zone 6. Even with significant winter leaf burn, these trees can make a strong comeback during the growing season in more northerly areas, such New Jersey, southern Ohio, and southern Connecticut.
Primary uses for southern live oaks are providing food and shelter for wildlife. Among the animals for which live oak acorns are an important food source are the bobwhite quail, the threatened Florida scrub jay, the wood duck, yellow-bellied sapsucker, wild turkey, black bear, various species of squirrel, and the white-tailed deer. The tree crown is very dense, making it valuable for shade, and the species provides nest sites for many other species.
The live oak is the larval host plant for the hairstreak butterfly and oakworm moth.
Live oak wood is hard, heavy, and difficult to work with, but very strong. In the days of wooden ships, live oaks were the preferred source of the framework timbers of the ship, using the natural trunk and branch angles for their strength. The frame of USS Constitution was constructed from southern live oak wood harvested from St. Simons Island, Georgia, and the density of the wood grain allowed it to survive cannonade, thus earning it the nickname "Old Ironsides". Even today, the U.S. Navy continues to own extensive live oak tracts.
Southern live oak is cultivated for shade and as an ornamental. Care is relatively easy, as it requires very little watering while it is young. After it is four to five feet tall, watering can be forgotten, and no more care is required. It is long-lived; trees in excess of 500 years were once common.
- The Seven Sisters Oak is the largest certified southern live oak tree.
- The Angel Oak on Johns Island, South Carolina, near Charleston is estimated to be in excess of 1500-years-old. It has a trunk circumference of 28 feet (8.5 m), height of 66 feet 6 inches (20.27 m) and limb spread of 187 feet (57 m).
- The Big Tree an estimated 1000-year-old southern live oak located in Rockport, Texas, the largest live oak in Texas.
- The Boyington Oak, an approximately 180-year-old southern live oak in Mobile, Alabama that is known for the folklore surrounding its origin.
- The Cellon Oak, with a circumference 30 feet (9.1 m), a height of 85 feet (25.9 m), and an average crown spread of 160 feet (48.8 m), is the largest recorded live oak tree in Florida. It is used as the logo of Alachua County, Florida.
- The Duffie Oak, a more than 300-year-old southern live oak in Mobile, Alabama has a trunk circumference of 30 feet 11 inches (9.42 m), height of 48 feet (15 m) and limb spread of 126 feet (38 m). It is the oldest living landmark in the city.
- The Emancipation Oak, on the campus of Hampton University in Virginia, is listed as one of the "Ten Great Trees of the World" by the National Geographic Society.
- The Evangeline Oak in St. Martinville, Louisiana.
- The Friendship Oak is a 500-year-old southern live oak located on the Gulf Park campus of the University of Southern Mississippi in Long Beach, Mississippi.
- The Toomer's Oaks, two approximately 75-year-old southern live oaks located adjacent to Toomer's Corner at Auburn University in Alabama, were at the center of an Auburn Tigers football tradition since the 1950s. They were poisoned by a vandal in February 2011.
- The Treaty Oak in Austin, Texas.
- The Treaty Oak in Jacksonville, Florida.
- Q. virginiana was first described and published in the Gardeners Dictionary, Edition 8. London. Quercus no. 16. 1768. "Plant Name Details for Quercus virginiana". IPNI. http://www.ipni.org:80/ipni/idPlantNameSearch.do?id=324846-2. Retrieved July 19, 2010.
- "Quercus virginiana Mill.-- The Plant List (2010). Version 1. Published on the Internet". www.theplantlist.org/. http://www.theplantlist.org/tpl/record/kew-175726. Retrieved 22 June 2011.
- Bender, Steve, ed. (January 2004). "Quercus virginiana". The Southern Living Garden Book (2nd ed.). Birmingham, Alabama: Oxmoor House. ISBN 0-376-03910-8.
- "Quercus virginiana in Flora of North America @ efloras.org". www.efloras.org. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501097. Retrieved 2008-11-01.
- Nelson, Gil (1994), The Trees of Florida: A Reference and Field Guide, Sarasota, Florida, USA: Pineapple Press, p. 84, ISBN 1-56164-055-7
- Kurz, Herman; Godfrey, Robert K. (1962), Trees of Northern Florida, Gainesville, Florida, USA: University Press of Florida, pp. 103–104, ISBN [[Special:BookSources/978-0-8130-0666-X|978-0-8130-0666-X]]
- "Selecting Tropical and Subtropical Tree Species For Wind Resistance". University of Florida IFAS Extension. University of Florida. http://edis.ifas.ufl.edu/pdffiles/FR/FR17500.pdf. Retrieved November 13, 2012.
-  "The USA National Phenology Network — Quercus virginiana", Retrieved 2011-07-06
- "Landowner Fact Sheets - live oak". www.cnr.vt.edu. http://www.cnr.vt.edu/dendro/LandownerFactsheets/detail.cfm?Genus=Quercus&Species=virginiana. Retrieved 2008-11-01.
-  "Some Reflections on the South Florida of Long Ago", Retrieved 2011-07-06
- "History of the Angel Oak". http://www.angeloaktree.com.
- Sledge, John S. (1982). Cities of Silence. Tuscaloosa, Alabama: University of Alabama Press. pp. 15, 19. ISBN 0-8173-1140-8.
- Pruitt, Paul M.; Higgins, Robert Bond (1963). "Crime and Punishment in Antebellum Mobile: The Long Story of Charles R. S. Boyington". Gulf Coast Historical Review 11 (Spring 1996): 6–40.
-  "Fun 4 Gator Kids — Cellon Live Oak", Retrieved 2011-07-06
-  "Cellon Oak Park", Retrieved 2011-07-06
- File:AlachuaCountyLogo.jpg "Alachua County Logo", Retrieved 2011-07-06
- Borland, Timothy (July 22, 2011). "Treehugger 4: Duffie Live Oak". Mobile Bay Magazine. PMT Publishing. http://www.mobilebaymag.com/Mobile-Bay/Bay-Buzz/Blog-2011/Mobile-Tree-Hugger-Part-II/. Retrieved November 13, 2012.
- Evangeline Oak Louisiana Historical Marker
- Jeremy Henderson (January 5, 2012). "Toomer’s Oaks old, but much younger than originally thought according to new study". The War Eagle Reader. http://www.thewareaglereader.com/2012/01/toomers-oaks-old-but-much-younger-than-previously-thought-according-to-new-study/. Retrieved September 11, 2012.
- "Toomer's Corner Oaks". Office of Communications and Marketing. Auburn University. http://ocm.auburn.edu/news/oaks.html. Retrieved September 11, 2012.