Skip Navigation

10.3: Toxicodendron diversilobum: Pacific Poison Oak

Difficulty Level: At Grade Created by: CK-12
Turn In

Common Name

  • Pacific Poison Oak
  • Western Poison Oak
  • Poison Oak


Toxicodendron diversilobum, or poison oak, can both grow as a shrub and a vine. It’s leaves are made of three leaflets with small teeth on each of the leaflets. They are two to six feet in height. If it gets hold of a sapling, or new tree, it could possibly kill it. When you touch it, the sap from it gets on your skin, eventually causing an allergic reaction that feels like a stinging sensation. It takes 100 nanograms of the allergen urushiol to get a reaction in more sensitive people. Also, this plant, as well as poison ivy, cause very painful reactions. So it’s a good idea not to touch poison ivy or poison oak, and especially to be careful in areas such as abandoned mines, forests, near rivers, ghost towns, and abandoned fields, which is where they flourish. The plant blooms in March and April.

The complete taxonomic classification is:

  • Kingdom: Plantae
  • Phylum: Magnoliophyta
  • Class: Magnoliopsida
  • Order: Sapindales
  • Family: Anacardiaceae
  • Genus: Toxicodendron
  • Species: T. diversilobum


Western poison oak appears at the southwestern point of Canada, stretching down through the Pacific Coast down to Baja California. They grow in moist soil with plenty of sunlight in elevations below 1,650m. There are some other sightings of western poison oak in other regions of California and some unregistered sightings of western poison oak in Nevada.


Cell Biology

As a member of the Kingdom Plantae, T. diversilobum is made of eukaryotic cells. The cells of T. diversilobum have a protective barrier called the plasma membrane. They are also made of many organelles, structures like small organs that help the cell function. The nucleus contains the DNA with instructions for the cell, making it a eukaryotic cell. mRNA is produced by the nucleus, and ribosomes translate mRNA into proteins. The mitochondria produces ATP (adenosine trisphosphate), which powers the cell. Vesicles transport materials within the cell or outside the cell. Lysosomes, a type of vesicle, take all the waste from the cell and takes it away. Endoplasmic reticulum is split into two parts, the rough endoplasmic reticulum and the smooth endoplasmic reticulum. The rough endoplasmic reticulum has ribosomes attached to it which create proteins that are released inside of the endoplasmic reticulum. It is then sent to the Golgi apparatus. The smooth endoplasmic reticulum creates lipids. The Golgi apparatus tells where the proteins from the endoplasmic reticulum where to go. The cytoskeleton gives the cell it’s shape. Since T. diversilobum is a plant, it has a couple of extra organelles. One is a large, central vacuole that stores the cell’s water and nutrients. The cell wall acts as extra protection in addition to the plasma membrane and provides structure. Chloroplasts make the plant green and allow for photosynthesis.

T. diversilobum cells divide by mitosis, where the nucleus divides, and the new cells have the same chromosomes (they are genetically identical) as their parent. Another way that cells divide is through meiosis, where the new cells have only half the chromosomes of the parent cell.


The first plant ever was ancestral green algae. The first plants that were found on solid ground were bryophytes such as hornworts, liverworts, and mosses. They were low-growing plants since they didn’t have any vascular tissue. Vascular tissue are tubes inside the plant that carry nutrients and water to the leaves so that they can use photosynthesis. They also carry the sugar made by the photosynthesis to other parts of the plant for storage. Ferns and some similar plants have vascular tissue which helps them grow tall. These plants reproduce with spores, and the spores need moisture.

After the ferns came the gymnosperms. Some gymnosperms include pines and firs. Their seeds are enclosed in cones but not completely enclosed. The last of the phases in evolution is the flowering plants. They produce seeds after having their flowers pollinated. Their seeds are inside the part of the flower that becomes the fruit. Flowering plants are the most abundant. T. diversilobum is a flowering plant.


There are many animals that can eat T. diversilobum, such as deer, rats, sheep, and goats. Birds would eat then disperse T. diversilobum seeds.

Anatomy and Physiology

T. diversilobum is a dicot, which means that it has both female and male reproductive systems on the same plant. As T. diversilobum is a vine, it has a long stem that have other stems coming out of the main vine. The leaves then come out of those smaller stems. It’s leaves are made of three leaflets with small teeth on each of the leaflets. Its sap contains urushiol, which can cause an allergic reaction. T. diversilobum has tiny, white flowers.




  • John D. Carpenter
  • Andoni Sanguesa

Supervising Faculty

  • Amy Huff Shah


  • Museum School, San Diego, California


  • Published prior to review.

Edit History

  • Created: April 5, 2013
  • Version 1.0 submitted to CK-12: July 4, 2013
  • CK-12 edits: in progress


  • Middle School (grades 6-8)

Opening image copyright by Ralph Loesche, 2011. Used under license from Shutterstock.com.

Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes
Show More

Image Attributions

Show Hide Details
6 , 7 , 8 , 9 , 10 , 11 , 12
Date Created:
Jul 18, 2013
Last Modified:
Feb 09, 2015
Files can only be attached to the latest version of section
Please wait...
Please wait...
Image Detail
Sizes: Medium | Original