Darrell Blackwelder: Poison oak and Ivy

Published 12:00 am Saturday, May 18, 2024

A friend of mine called me the other day, concerned about poison oak in her flower bed. She had cleared it from the beds last year, but it had returned this spring. Her granddaughter had succumbed to the skin irritant last year while working in her garden. In severe cases, the skin rash (dermatitis) may hospitalize its victims. Identification and control of poison ivy is one step in prevention of dermatitis.

Poison ivy is commonly found in undergrowth in wooded areas, fence rows, cleared lots or growing as a vine on trees.  The vine may grow as a low-growing shrub in the absence of trees or other support objects.

The stems of poison ivy are smooth, light brown to gray. The leaves are very ornate and shiny with broad serrated margins. The leaves are trifoliate, (groups of three) producing gray-white berries 1/4 inch in diameter. These berries are a favorite food of birds and a major source of seed distribution.

The poison is on the leaves and stems but also found in the roots, bark and berries. It’s an oily substance that does not dissolve in water and easily adheres to many objects including pet fir, clothing, garden tools, golf clubs, guns or fishing rods. Smoke from burning stems or leaves is another source of irritant as is splashing sap from stems and twigs when cutting trees in the winter months while gathering firewood.

The susceptibility of dermatitis depends upon the individual. Minute amounts of the oil can cause a rash. The poisonous oil penetrates skin tissues creating sensitive tissues.

Now is an excellent time to control poison ivy. The best time to control poison ivy is just before and after bloom in the early summer. Brush killers or herbicides that contain dicamba or trichlopyr (2,4-D) effectively controls poison ivy. Glyphosate or Roundup will also kill the vine.

Carefully follow the instructions provided on the label. Contact the Cooperative Extension Service if you have questions about applying any pesticides. More detailed information on poison oak and poison ivy can be found online at https://caldwell.ces.ncsu.edu/2022/05/poison-ivy-identification-and-control/

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu.