How to Get Rid of Poison Oak Plants
Identification, Killing Poison Oak Plants With Herbicides
How do you get rid of poison oak plants? Well, sound eradication methods begin with positive identification, so let's begin with that.
"Leaves of 3, let them be" is the familiar warning that applies both to poison ivy and to poison oak. But telling the two apart is easy: poison oak has leaves shaped like the leaves found on oak trees. The leaves of both poison oak and ivy turn red in fall, and both plants produce white berries. Poison oak vines (or, sometimes, shrubs) are indigenous to North America.
In the U.S., poison ivy (Rhus radicans) grows everywhere but on the West Coast, while poison oak (sometimes misspelled as "poisen" oak or "posion" oak), or Rhus diversilobum, grows primarily on the West Coast. In the taxonomy of these plants they are sometimes classified as Toxicodendron rather than Rhus ("Toxicodendron" is from the Greek and literally means "poison tree").
Methods for Getting Rid of Poison Oak
Okay, now you have a better idea of what you're dealing with. But how do you get rid of poison oak? I'll discuss three options you can use to kill poison oak:
Getting rid of poison oak manually.
Applying herbicides to the cut stumps of poison oak.
Applying herbicides to the leaves of poison oak.
You should obviously try to have as little of your skin exposed as possible when getting rid of poison oak, since it is through physical contact with the plant (any part of the plant!) that the rash is contracted. At the very least, this means wearing gloves, long-sleeved shirt and full-length pants.
The object in trying to get rid of poison oak manually is to pull it out by the roots. The roots must be disposed of; do not burn! Inhaling fumes from burning poison oak causes far greater health problems than just the rash caused by skin contact. Another manual method for getting rid of poison oak (if it is growing on the ground, rather than in trees) is to smother it. Smothering entails cutting it back close to the ground, then placing newspapers, cardboard, old carpeting, tarps, mulch or some other covering on top of it. However, be aware that, even after they are killed, the plants remain toxic. So be careful in disposing of the roots of the dead plants after pulling back the smothering agent (even if you've waited for years). Manual eradication may have to be repeated. Note that manual methods may be practiced at any time of the year (except during winter in the North, when the ground is frozen), whereas methods involving herbicides are best employed during the height of the growing season.
Examples of herbicides that may be used for killing poison oak are glyphosate (e.g., the Roundup brand) and triclopyr (e.g., the Ortho brand).
Wielding your trusty pruners and a can of herbicide, you can apply the herbicide to the cut stumps of poison oak while the plant is actively growing. Cut the stem an inch or two above the ground and apply the herbicide right away. The fresh wound will drink in the herbicide, transporting it deep inside where it can do its damage.
Applying herbicides to the leaves of poison oak is most effective during the flowering stage (with triclopyr) or fruiting stage (with glyphosate). Such "foliar spraying" will have to be repeated until the poison oak is fully eradicated. Here's how to spray:
You'll need a tank sprayer; mix the product with water, according to directions.
Pick a day with little or no wind for spraying. Also, check your forecast: don't spray if rain is predicted at any time within the next 24 hours.
For poison oak growing on the ground or on a wall, heavily spray the leaves and vines.
For poison oak climbing up a tree, you may wish to "paint" the herbicide on, so as to preclude damaging the tree with a stray mist from your sprayer.