Dangers in the Garden - Part 3

Irritating Plants by R. Lieber

Problem plants are rarely life threatening even if poison is in their name. Poison Ivy, Poison Oak and Poison Sumac, are all found in Tennessee and can induce uncomfortable rashes upon contact. Poison Ivy is the only one of the three commonly found in Blount County. Some people are not affected by poison ivy, but most of us develop itchy responses after a few exposures to the Urishiol oils in the plant. Any part of the plant can provoke the allergic reaction because these oils exist on the surface of the leaves, branches or vines.

Pets are not affected by urishiols, but oils brought in on their coats can provoke rashes in their owners on contact! Also, clothing that has been in contact with poison ivy can cause a reaction when touched in the course of laundering. Removing poison ivy from your landscape is key, but cleaning tools and gloves with soapy water after each use will help to prevent unintentional skin exposure. Most home remedy herbicides have no lasting effects on poison ivy that has established itself in the garden, so hand removal is the surest method, wearing disposable gloves and double-bagging the plant material. Burning and composting are not recommended. Urishiols can be carried on the smoke and irritate eyes and lungs.

Most of us have grown up with the "leaves of three – let it be" ditty to help identify poison ivy, but there are many similar looking vines and shrubs. Poison ivy will sometimes have smooth edged leaves and others times have serrated looking leaves. A distinct hallmark is the long "neck" or stem of the center leaf and a "mitten" shape to outer two leaves (where the thumbs point away from the center of the three-leaf shoot). Poison ivy will also have hairs along some of the stems which are actually rootlets. You may see a dramatic example of these rootlets where an old vine is clinging to a larger tree.

Another group of weeds and cultivated plants to be cautious around are part of the spurge family or Euphorbia. Most have a white or milky sap that can irritate skin. Euphorbia include spurges commonly seen as lawn weeds, e.g. prostrate spurge and spotted spurge. They also include cultivated perennials and the popular greenhouse plant Poinsettia. The family includes Crown of Thorns, Castor Bean plant and croton. All of them can cause skin irritation and, in some cases blindness, if the sap comes in contact with an eye.

Some spring blooming bulbs, including daffodils and hyacinths, have milky sap and will also cause skin irritation. Their poisonous and irritating qualities make them popular for deer resistance but can be dangerous to small children and pets.

Stinging Nettles have fine hairs on leaves and stems which can cause severe irritation to skin. Black Nightshade and Horse Nettles have thorns. Both look like spiky tomato plants with similar white flowers. They are most noticeable when their fruits ripen, turn a bright yellow-orange and look like mini-tomatoes.

Other nightshades include the silver leaf, which is a low growing silvery green plant with violet colored flowers. The 'buffaloburr' nightshade has similar oak-leaf-like leaves but has a brilliant yellow bloom and seed pods that have spiny thorns.

Another burr-forming plant, and a common pasture nuisance, Burdock, is dangerous to pets and livestock more than humans. The tenacious seed pods that inspired the invention of Velcro can cause irritation, infections and skin problems for many pets, and make livestock ill.

Pokeweed is another of the many weeds that pop up in local gardens and on farms. It is not as dangerous to adults as it to children and pets who are also more likely to ingest fruit off of the plant.


How to ID and eradicate poison ivy, sumac and oak in Tennessee: http://www.tnstate.edu/extension/documents/Poison%20ivy%20Fact%20sheet%20ANR-7.pdf


Memphis Master Gardeners fact sheet on all urishiol producing plants:


Clearing houses for pictures and information on poison ivy and its plant relatives:



Appalachian Region Noxious weed ID and how to control from UT:


Blount County Extension Master Gardeners

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