Rash Doctors

Many of the botanists of yore were primarily medical doctors by profession. Examples include such greats as Asa Gray, George Engelmann, John Torrey and to some extent Carolus Linnaeus himself. If modern doctors had such affection for our wild flora, perhaps I wouldn’t cringe when I commonly hear of people in the Midwest diagnosed with Poison Oak or Poison Sumac rash. To them, I usually reply with some cynically derived question regarding the geographical location of their encounter with the offender. If they have been diagnosed with Poison Oak I ask, “have you been in the forests, woodlands or swamps of the southern states lately?”. My Poison Sumac inquiry is more specific. “Have you been in a high quality wetland community lately?”, I say.

Most folks eye me queerly and retort “no, I was doing yard work” or “whatever do you mean”. The bait being taken, I explain that Poison Ivy is a much more likely explanation for their dermal discomfort; especially for those living outside the range of anything but Poison Ivy, as most Midwesterners are. Some, in true argumentum ad verecundiam fashion, defend their doctor’s claim. Others are interested in the difference and enjoy learning a bit of natural history. For those that don't know the difference.....

...here is Poison Ivy (Toxicodendron radicans).

Notice the sharp pointed teeth on the leaflet margins, the pointed tips of the leaflets and the long petioles of the lateral leaflets. Its habitat ranges from anywhere to everywhere; xeric to mesic, acidic to calcareous, disturbed to pristine, the PI can live there. Poison Ivy usually grows like a true vine. It clambers and twines on structures and other vegetation. It is common throughout North America in every state and province east of the Rockies.

Here are two photos of Poison Oak (Toxicodendron pubescens).

Notice the rounded teeth of the leaflet margins, the blunt tips to the leaflets, the nearly sessile lateral leaflets and the relatively long petiole of the terminal leaflet. Its habitat tends to be quality dry to mesic forest and woodlands. Poison Oak does not vine or climb on other vegetation but rather grows as a small shrub. Its geographic range is basically the southern states of the Civil War with a few stragglers into border states.

Lastly, here is Poison Sumac (Toxicodendron vernix).

Notice that the leaves are entire and pinnate instead of trifoliate –so much for the “leaves of three” adage. The habitat of Poison Sumac consists of quality fens, bogs and wetlands. It grows into a shrub of ten feet or so. It occurs sporadically throughout most of eastern North America.

So the next time the doc says “you have poison oak”, Get a second opinion and get it from a botanist.