Poison Oak? Please Don't!

Poison oak is generally the name of a plant (Toxicodendron pubescens); however, and though it may be hard for a quercophile to stomach, it can also refer to an activity. An incident involving the poisoning of oaks has been discussed in our publications before, and now IOS member Angela Moskow has shared a couple of items related to this practice.

A Quercus lobata growing in Woodland, California, died in 2020, apparently the victim of deliberate poisoning. It grew near the onramp to a state highway and it is suspected that it was killed by a new owner wishing to develop the land. You can read more details in a news story here.

After the oak was cut down, David Wilkinson, President of the Woodland Tree Foundation (quoted in the news story), was able to gain permission to enter the property and count the rings of the oak. He suspected it was an old tree, because he had been able to see it was already a large specimen by 1937, based on aerial photos provided by University of California (UC), Davis (Woodland is a few miles north of Davis, California). The ring count yielded an estimated age of 212 years.

Sad to think that the life of a venerable tree should be cut short in such a tawdry, banal manner. Woodland is home to many large oaks; according to Rolf Frankenbach, also of the Woodland Tree Foundation, several of the trees date to well before Anglo settlers came to the area around the time of the Gold Rush. This would also be true of the poisoned oak.

As if this story were not enough to feed quercicidal nightmares, Angela also shared a gruesome document published in 1959 in Down to Earth, a publication of the Dow Chemical Company subtitled "A review of agricultural chemical progress". It had been sent to her by Dr. Gary Adest, Founder and President of River Ridge Ranch & Institute. The article is authored by researchers from the UC’s Agricultural Extension Service and provides detailed instructions on how to kill oaks found in the grass-woodlands of California’s great valleys (Q. douglasii, Q. kelloggii, and Q. wislizeni). The authors mention several methods used to control oaks before recommending the “cut-surface treatment”, whereby herbicide (2,4-D) is applied directly to cuts in the bark made all around the tree and near the base of the trunk. The paper concludes with the sapcurdling sentence: "It is estimated that some 6,000,000 acres of our California woodland-grass foothill range could profit from such improvement." You can access the article by clicking on the image below. Viewer discretion advised.

Returning to David Wilkinson of Woodland Tree Foundation, Angela recommends a book David published in 2021: Gertrude’s Oaks: The History & Legacy of Woodland’s Urban Forest. You can read more about the book in a June 2022 issue of Oaks, a newsletter edited by Angela for California Wildlife Foundation/California Oaks. While there you can click on the button top right (Join Our Email List) to subscribe to this highly recommendable newsletter.