Native Plants

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Tuesday - August 27, 2013

From: Ellicott City, MD
Region: Mid-Atlantic
Topic: Plant Identification, Poisonous Plants
Title: Identity of plant with thorns in Maryland
Answered by: Nan Hampton

QUESTION:

I live in Maryland and was walking in the woods one day when I accidentally stumbled in to a thorn bush. I don't remember what color the thorns where or very much about the plant in general but I do know it hurt more than a normal thorn bush, and it kept hurting. It felt like it had an irritant on the thorns that made the cuts from it swell red, itchy, and painful. That went away after awhile but today I found two, large red dots on the side of my foot that had seemed to get bigger and more painful. I checked all insects and arachnids in the area but found none that could have caused it. Could it be the thorns? If so, do you know what kind of thorns they are? Thanks Mr. Smarty Plants.

ANSWER:

We have had questions before about plants with poisonous thorns. So far as I know there are no plants in North America with thorns that are poisonous or have an irritating substance associated with them. I am going to refer you to the most recent of those questions which also has references to earlier questions. You haven't given us enough information to identify what plant the thorns you encountered were on. There are plenty of plants with thorns in Maryland—Smilax bona-nox (Saw greenbrier), Rosa carolina (Carolina rose), Aralia spinosa (Devil's walkingstick), and Rubus allegheniensis (Allegheny blackberry) to name just a few—but without a description of the plant I can't even begin to identify the source of the thorns.

There are at least two possible explanations for the initial red, itchy, painful results of your encounter with the thorny plants and the subsequent red spots on your foot:

Dirt or other sources of bacteria were on the thorns and were transferred to you when the thorns pierced your foot and this caused the irritation and possibly an infection.
The tips of the thorns were broken off in your skin and are still there causing the irritation.