Poison Plants: What they Are and What To Do

If you were a Boy Scout, you probably learned the phrase, "Leaves of three, let it be.  Leaves of five, let it thrive."  Some may have also learned "Hairy vine, no friend of mine" and "Berries white, run in flight."  The "leaves of three" phrase refers to the poison ivy (Toxicodendron radicans) and poison oak (Toxicodendron pubescens) plants.  The key identifying feature of these varieties is a leaf that consists of three leaflets grouped together.  The leaves are glossy-green early in the growing season and then turn yellow to deep red in the fall.  The leaves are also distinguished by prominent mid-veins that divide each leaflet into equal sides with smaller veins evenly spaced at a 45 degree angle to the mid-vein.

Poison ivy can grow in a variety of forms, either as short shrubby plants that grow on the ground and spread by horizontal underground stems or as vines that can climb trees, walls, and poles.  The stems of the climbing vines have small aerial roots growing from the sides that give it a "fuzzy" or "hairy" appearance.  This characteristic is where the phrase, "Hairy vine, no friend of mine" originated.

Poison sumac (Toxicodendron vernix) is related to poison ivy and poison oak.  However, unlike the previous plants, the leaves have clusters of between seven and thirteen leaves.  Poison sumac can also have small white flowers that change to white berries.  This characteristic is where the phrase, "Berries white, take flight" originated.

Contact with the oil urushiol from these poison plants causes a rash, blistering, swelling, and extreme itch in sensitive individuals.  Up to 90% of people who come into contact with the oil will develop the rash.  While all parts of these poison plants contain urushiol, most people come in contact by brushing up against the leaves.  However, contact with stems and vines even during the winter may affect sensitive individuals.  You don't have to be exposed to much of the oil - as little as 50 micrograms of urushiol (an amount smaller than a grain of salt!) is enough to cause a reaction.  The rash, generally called contact dermatitis, can also be spread through contact with the urushiol oil on freshly contaminated clothing, gloves, and footwear.  You can become sensitive to the oil at any point in your life, even if you have never reacted to it in the past. 

If you find yourself having a reaction to poison ivy, poison sumac, or poison oak, you can try to treat the sores at home with a topical hydrocortisone cream.  Try not to scratch or irritate the sores as the infection may spread.  Some people take oatmeal baths to calm down the itchy irritated skin.  If that does not help, you can visit your doctor or a walk-in clinic.  They can give you a steroid shot to help jumpstart the healing process.  You may also receive a prescription steroid cream to use on the affected skin areas.  If those are not adequate to heal the sores, you may then be prescribed an oral steroid, such as prednisone.  

To prevent future poison ivy, poison sumac, or poison oak reactions, learn what these plants look like so you can avoid them.  When doing yard work, make sure you wear long pants, long sleeves, and gloves to prevent the urushiol oil from getting on your skin.  Be careful with pets as well.  While dogs and cats do not react to the oil from these plants, pets running in poison ivy may inadvertently carry the oil on their fur, potentially causing problems to humans who pet the animals.

If you know where these poisonous plants grow in your yard, you can try to safely remove them to prevent future reactions.  The woody vines should not be burned because heat volatizes the oil; the contaminated smoke can get into your eyes and lungs, potentially causing a more serious problem than physical contact.  Vines growing up objects can be severed near the ground and allowed to shrivel and die.  Afterward, the root and new growth that it will produce can be more easily managed.  Broad spectrum nonselective herbicides such as glyphosate (Roundup) or triclopyr (Ortho Poison Ivy and Tough Brush Killer) may be used to chemically control poison ivy.  Since these products are nonselective, take care not to apply them to other nearby plants.