PPDL Picture of the Week for

August 17, 2015

Poison Ivy: A Known But Often 

Misidentified Pest​

Travis Legleiter, Weed Science Professional Assistant, Botany & Plant Pathology Department

Everybody has heard of it and many people have dealt with the itchy, scratchy, oozing consequences of touching it, but a lot of people cannot identify poison Ivy.  We all know the rash that poison ivy can leave on your skin and many of us know first hand how irritating and painful it can be.  Once you have been exposed to poison ivy and made contact with its irritating oils all an individual can do is wait out the rash usually along with the help of lotions, ointments, and in worse case scenarios prescription steroids.  Although simply being able to identify poison ivy and thus being able to avoid it is the ultimate way to avoid the nasty rash that it leaves on your skin.
Poison ivy is a vining plant that tends to prefer areas with other vegetation that it can grow on, such as fencerows, and thus can often be inconspicuous as it grows on and along side other plants.  Although it’s unique leaf pattern, leaf margins, and typically shiny leaves should be a key for picking it out amongst other green foliage.  

Poison Ivy can be identified by a couple of characteristics, starting with it three leaflet compound leaf.  The leaf has three leaflets arranged with two of the leaflets opposite of each other on short to none existent petioles, while the third leaflet will be on the terminal or end of the leaf on an extended petiole.  This unique three-leaf pattern should not be confused with any other three-leaflet plants.  The next characteristic is the uneven serrations on the leaf margins.  The serrations of toothed edges of the leaves will be uneven from ones side to the next, often with one side heavily serrated and the other completely without serrations.   The uneven serration along with the three-leaflet structure will distinguish poison ivy from all other species found in Indiana.  

A couple of other characteristics that may help you pick out poison ivy from the other vegetation is it often has a shiny waxy surface to the leaves and can often be red tinged in color.
If you are ever in doubt if a plant is poison ivy or not it is probably best to avoid it. Also always stay attentive to all vegetation when you are in a heavily wooded and vegetative area as these are areas where poison ivy is likely to occur.

​Click image to enlarge

Figure 1.-Three leaflet compound leaf of poison ivy.  Also note the uneven serrations on each of the leaflets in which the opposite sides of the leaves do not match.
Figure 2.-The three leaflet compound leaves of poison ivy.  The newest leaves often have a reddish tinge and appear to be shiny.