Toxicodendron diversilobum (T. & G.) Greene                                                     = Rhus diversiloba   Anacardiaceae                                                 Sumac Family                                                            Native   Poison Oak

                                             June Photo

Plant Characteristics:  Deciduous tree, shrub, or woody vine with poisonous properties; 1-2 (-3) m. tall, stiffly branched, sparingly pubescent or glabrous; lvs. alternate, pinnately 3-foliate, the lfts. opposite except for the terminal one,  obtuse, usually crenulate or even lobed, ovate to sub-orbicular, 2-7 cm. long, bright green and shining above, paler beneath; panicles axillary, racemose; petals of male fls. 3-4 mm. long, of female 2-3 mm.; fr. whitish, glabrous, subglobose, 4-7 mm. thick; seeds flattened, 3-6 mm. long, irregularly roughened.

Habitat:  Common in low places and thickets and wooded slopes below 5000 ft.; Coastal Sage Scrub, Chaparral, etc.; cismontane; to Wash., L. Calif.  April-May.

Name:  Latin, toxico, poisonous, and dendron, tree;  (Munz, Flora So. Calif. 67).   Diversilobum means diversely lobed.  (Dale 45).

General:  Common on the west side of the bay southerly the Delhi ditch and along the path to 23rd St.  Very common on the bluffs at the north end of East Bluff.  Photographs from both areas.  It is interesting to note the differences in plants located across the bay from each other.  On the Eastbluff side, the leaves are thinner and the plants more trailing than on the west side where the plants are shrubby, and in some cases tree-like; the leaves there are thicker when mature. (my comments).      This plant can be an erect shrub to 3 meters tall or climb by means of aerial rootlets, (Rhus radicans) or have 5 leaflets, Rhus quinquifolia.  Bees visit the plant, but their honey contains no poison.  The most widely spread shrub in Calif.  (Robbins et al. 292).       Indians are reported to have eaten the leaves in the spring in the hope of building an immunity to the plant.  The same tribe's remedy for blisters caused by the plant poison was to wash the area with boiled Manzanita leaves.  (Balls 61).      Another tribe used the juice from the plant to cure warts, ringworm and snakebites.  (Dale 45).     Northern Calif. Indians (the Pomo for one) used the juice in tattooing.  A design was drawn on the face with poison oak juice, then soot was pricked in with a sharp pointed needle from the nutmeg tree.  This gave a blue-green color, unfading.  (Murphy 56).     A black stain was made from the juice.  (Heizer and Elsasser 136).      The slender stems of poison oak were used in woven baskets.  (Bauer 159).      The sticky sap of both poison oak and poison ivy contain a mixture of chemicals called catechols, which cause an allergic skin rash.  The very worst cases of poison oak and poison ivy occur when the plants are burned.  The toxic oils are carried by the smoke and settle on everything in its path.  If the smoke is inhaled, a rash may develop inside the lungs.  There is no truth to the common belief that one can contract a case of poison ivy by touching the blisters of someone who already has the rash.  Strictly speaking, these plants are not truly poisonous, instead the rashes that they produce are allergic reactions--poison oak poisoning is an allergy.  This is why some people may  handle these plants and never suffer the slightest ill effect.  Doctors estimate that more than half of the people in the United States are allergic to poison oak or poison ivy, making this one of the most common allergies known.  When touched, the sap is quickly absorbed by the skin--the entire process takes about ten minutes.  (Eshleman 93,96,97).     The Indian tribes of the Santa Barbara area were called the Chumash.  One of the plants they used medicinally was Toxicodendron diversilobum, poison oak.  It was taken internally as a remedy for dysentery or diarrhea.  The root was boiled--taking care not to let the vapor get into the eyes lest blindness result--and the decoction drunk cold.   Mission records from the early 19th century state that plasters of powdered poison oak were very effective in healing wounds and lacerations.  One hundred years later, poison oak juice was still being applied to staunch the flow of blood from a cut.  Apparently Indian peoples generally did not experience the severe contact dermatitis which affects many contemporary Anglo Americans following contact with poison oak leaves and stems.  (Timbrook, J. "Virtuous Herbs: Plants in Chumash Medicine".  Journal of Ethnobiology, Winter 1987, 171-180).       According to Romero (1954:63), the roots of poison oak were gathered , cut, dried and used to make a tea.  Taken in small quantities, the tea was said to render one immune  to poisoning by poison oak.  Cahuillas, Indians of the Colorado Desert, the San Bernardino and San Jacinto Mountains, interviewed by the author failed to recall any such use.  (Bean and Saubel 132).      Ivy Block, the first poison ivy, poison oak and poison sumac protectant approved by the U.S. Food and Drug Administration is produced by Enviroderm, a Louisiana pharmaceutical company.  It is applied to the skin about 15 minutes before contact with the plant is likely and works by preventing urushiol, the oily substance that creates blisters and inflammation, from reaching the skin in toxic form.  Urushiol can linger on clothing, garden tools, and even pets, who are immune to the plants irritants.  The oil is then spread onto rugs or furniture and may remain toxic for up to a year.  Tecnu, a product designed in the cold war era to wash off radioactive debris, can help minimize the reaction of urushiol if used within eight hours of exposure.  Neither Tecnu nor Ivy Block cures the poison ivy rash.  (Cohen, Warren.  "Poison ivy suddenly gets a lot less scary."  U.S. News & World Report July 6, 1998, pp. 70-71).     Often conspicuous in the dry season by its red foliage.  Munz, (Flora So. Calif. 67.)     Munz, Flora So. Calif. does not say anything about the number of species of Toxicodendron.      Hickman, Ed. says 6 species of America and e. Asia p. 136.

Text Ref:  Hickman, Ed. 136; Munz, Calif. Flora 998; Munz, Flora So. Calif 67.

Photo Ref:  May 4 83 # 8,10; June 7 83 # 7A,8A; Mar 1 84 # 8.

Identity: by R. De Ruff.  

First Found:  May 1983.

Computer Ref:  Plant Data 128

Have plant specimen.

Last edit 6/12/05.

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