Oh my, I thought to myself, of all the days to wear shorts.
Warily I beheld the botanical nightmare that stretched before me. A massive patch of plants was located above my head. As I glanced further down the road, I could see even more clusters. They were growing right alongside the edges of the sidewalk. I recoiled instinctively.
Fortunately, I knew I hadn’t yet come into physical contact with this plant. So for now at least, I was safe. But my sense of contentment was gone as I took in the sight before me. I couldn’t help but admire the slender grayish-brown stems bearing lobed green leaves.
Though they appeared as innocent as the oak leaves they resembled, I knew the truth. I knew that one brush of my bare skin against their shiny, oil-covered leaves would leave me in agony. An all too familiar rhyme ran through my head.
“Leaves of three, let them be. Poison Oak do I see.”
Toxicodendron diversilobium, more commonly known as the Western or Pacific Poison Oak, inhabits plant communities throughout the western United States according to Melissa Petruzzello of Britannica. This plant’s remarkable hardiness enables it to inhabit a wide variety of habitat types.
The Las Palitas nursery claims that some of the plant communities in which poison oak can be found include “chaparral, coastal sage scrub, mixed-evergreen forest, northern coastal sage scrub, northern and southern oak woodland.”
Poison oak is described by the Oregon State University College of Agricultural Science’s Department of Horticulture as a broad-leafed plant that can take the form of a woody vine or shrub. The variability of forms that can be witnessed within poison oak is, according to the California Native Plant Society Calscape, depend upon the amount of sunlight the plant has access to.
In areas with partial to full shade, it will often take the form of a woody climbing vine. In areas with full sunlight poison oak will frequently form dense aggregations of multi-stemmed shrubs.
Act for Libraries.org’s article Facts About Poison Oak state that, “The Latin ‘diversilobium’ refers to the extreme variability of the poison oak leaves.” These leaves often appear shiny or glossy thanks to the presence of an oil called urushiol.
The common rhyme used to help identify poison oak, “leaves of three, let them be” refers to the fact that the leaflets are arranged in pairs of three. In the springtime, this plant bears small white or yellowish-green flowers that form white or light brown colored fruit in the summer to early winter.
As the seasons’ change in the fall, poison oak will develop a striking red to reddish-gold color within its leaves. The smooth, naked grayish-white to light brown bark forms distinctive stands of woody sticks in the wintertime.
Unfortunately, this deciduous plant can be problematic for humans throughout the year. Samantha Caveny in her article Poison Oak: Identification and Treatment: What’s the Difference Between Poison Oak and Poison Ivy?, illustrates that the skin-irritating urushiol oil is not limited to the leaves of the plant alone.
This oil, which causes an allergic reaction within the skin that develops into a form of contact dermatitis, can be found in every part of the plant. That means the risk of coming into contact with the urushiol oil is a year-round risk.
Ann Pietrangelo of Healthline also warns in Poison Oak Rash: Pictures and Remedies that “the oil can be contagious. {Causing} an allergic reaction by touching the plant, but also clothing or other objects that came into contact with the plant”. WebMD recommends that medical treatment be sought if the rash continues to worsen, spread to cover a large percentage of your body, or if new symptoms such as fever and swelling occur.
The relationship between humans and poison oak is complicated.
I could completely understand why so many people loathed the plant and wished that it didn’t exist within the natural areas and parks. Many people probably wouldn’t mind if it was wiped off the face of the earth. Yet few plants give back to the natural world as much as poison oak does.
Poison oak is a valuable resource for more species of wildlife than one would imagine. Many species of birds and mammals can utilize the plant for food and shelter according to Act for Libraries. Even pollinators can utilize the flowers as a source of food in the springtime, and some species of bees may even depend upon poison oak.
Often an early colonizer in disturbed landscapes, as described by botanist William Gillis of Michigan State University to Bay Nature Magazine, can aid with habitat mitigation by creating habitat structure for wildlife and out-shading non-native plants. More importantly, this plant is a valuable tool for restoration efforts as a nurse plant.
According to the Cosumnes River Preserve, poison oak “{helps} to establish the growth of other plants growing alongside them under the valley oaks or other trees that grow native in the area”. Who could imagine that a plant as despised by outdoor enthusiasts as the poison oak plant, could be the key to restoring our natural world?
I turned back to the poison oak patch for one last glance and noticed it was flowering. I didn’t see any bees circling the small blooms, but I understood enough to be able to imagine the cycle that would emerge. After pollination, the flowers would form small fruits that helped to feed the birds who would build nests within the shrubs.
Those birds would spread the seeds far from the parent plant, forming new patches of poison oak. Communities that could help the native seed bank lying quietly underneath the soil awaken. Bringing back some of the landscape that had been lost.
Perhaps we all would be better served if we could look beyond the complicated relationship between humans and poison oak. If we could remember the many virtues of this plant, and see it not as a pestilence, but a gift to the land.
