Q: Recently my wife and I were at a restaurant. I saw there a plant identified as a pencil tree. I asked for a cutting. The wound produced a white, sticky sap which got on my fingers and which I accidentally rubbed in my eyes. At once there was trouble: severe burning and watering, blurred vision, dizziness and confusion. At the emergency room I was told that I had latex poisoning and that if immediate medical attention had not been given, corneal damage and possible blindness could have resulted.

A: Your pencil tree, ^Euphorbia tirucalli^, is well known to produce a particularly caustic sap. Any plant in the ^Euphorbia^ genus should be considered poisonous. Even though poinsettia, ^Euphorbia pulcherrima^, has been shown not to be dangerous, the sap should be avoided.

Another plant juice to avoid is that of elephant ear. It is a member of the arum family, as are spathiphyllum, dieffenbachia and caladium. All have sap that contains calcium oxalate crystals, which causes “oral irritation; intense burning and irritation of the mouth, lips, tongue; excessive drooling; vomiting; and difficulty in swallowing” when ingested.

Plants have many ways to protect themselves beyond thorns and prickles. Your experience is a caution to us all.