Scientific Name
Toxicodendron diversilobum (Torrey & A. Gray) E. Greene
Family
Anacardiaceae
General
This plant is not a true oak, but rather more closely related to member of the genus Rhus (also found around CI) and poison ivy. It grows as a low shrub. The common name comes from an oil it produces which upon contact causes sever blistering and persistent itching (SMN is writing here from personal experience). After the Springs Fire of May 2013, the offending oils were still active enough to illicit a minor response (again on SMN), even though the plants had been reduced to ash. Anyone hiking in natural habitats in Southern California would do well to learn this plant – and avoid it. Rubbing mugwort (Artemisia douglasiana) into affected areas is said to partially alleviate the blistering. Likewise, rubbing find sand or soil onto the exposed skin immediately after exposure will carry away some of the oils before they can have their full effect.
CI
On campus habitats, Toxicodendron diversilobum grows in dense patches usually on north facing slopes near the base of large rock faces. Perhaps this species requires the extra rain water that concentrates on such sites. It is not present in more open or exposed areas.
References
See this species on CalFlora.
The Jepson Manual (2012:171, Anacardiaceae, John M. Miller and Dieter Wilken).
Dale (2000: 44)
McAuley (1996: 171).
Toxicodendron diversilobum on hillside to south of University Glen, CI (7 February 2013).
Toxicodendron diversilobum on hillside to south of University Glen, CI (7 February 2013).
Toxicodendron diversilobum among jumble of large boulders to the northeast of Sage Hall, CI campus (11 December 2014).
Toxicodendron diversilobum a large attractive stand growing near base of hill, against large rock face, to south of University Glen, CI campus (13 June 2014).
Toxicodendron diversilobum north face of hill, near crest line in shade of large jumble of boulders, to south of model airplane field, University Park (18 March 2015).
Toxicodendron diversilobum at base of rock face on north slope of hill at southern margin of University Park, south west of model airplane field, University Park (1 June 2016).
Toxicodendron diversilobum north face of hill, near crest line in shade of large jumble of boulders, to south of model airplane field, University Park. Note fire damage shrub and burn marks on the rocks (20 May 2014).