   Poisonous Plants - December 7, 2005 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County More than 700 species of plants located in the United States and Canada have caused illness or death in humans. In native plant populations, the presence of toxic compounds largely can be explained by natural selection. Plants containing toxic compounds are less likely to be grazed by animals and arthropods. Over time, less palatable (more toxic) plants in a given species’ population are more successful and the genes that produce these toxins are passed on to future generations. By the same process, animals and arthropods have also become more tolerant to low levels of toxins through time. Many vegetable plants also contain toxins. Selective breeding has decreased toxin content of vegetable crops to tolerable levels. For example, the stems and leaves of tomatoes, potatoes, peppers, and eggplant (members of the Nightshade family) contain glycoalkaloid toxins: the primary one being solanine. The edible fruits and tubers of these plants do not contain toxic levels of glycoalkaloids. However, potatoes may turn green in response to light exposure and become toxic. Nicotine is also a glycoalkaloid found in tobacco, another member of the Nightshade family. Other poisonous plants cause dermatitis. In the Verde Valley, we have poison ivy (Toxicodendron radicans) along the river, creeks and ditches. It is not common, but creek walkers should learn to recognize and avoid it. Most people know that wild mushrooms can also contain deadly toxins and persons not able to positively identify the various species should not harvest or eat them. Most plants we use in landscapes were selected from wild populations for various qualities including foliage, flowers, and scent. In some cases, little or no consideration is given to a plant’s toxic qualities. In another sense, a poisonous landscape plant is also more resistant to herbivory by animals and arthropods which in turn could reduce wildlife conflicts and pesticide applications. Regardless of whether you care about why plants are toxic, most people care which plants are toxic. There are lists of poisonous plants, but this assumes that you can identify the plants in your home and landscape. Knowing your plants is a good long-term goal, but the following practices can help you, your family, livestock, and pets avoid plant poisoning. In the home, children need to be taught not to eat any part of a plant unless they have permission from a knowledgeable adult. Decorate with plants that are not poisonous. Children love to play with plants in the yard. Explain that plants can be played with, but not eaten. Tell children not to eat mushrooms and that they are not the same mushrooms you buy in the grocery store. Gardening is often a family activity. Until you use seeds and bulbs, store them safely out of reach of children. Explain that when the plants grow, the fruits and vegetables will be picked together. Children should not pick any vegetables or fruit without supervision. They may confuse good food with that which is harmful. Do not use plants to make potions, medicines or tea unless you are trained in this area. Avoid smoke from burning plants. Ingesting plant products and inhaling plant smoke could be harmful. If there is a suspected human plant poisoning, immediately contact a physician or the Arizona Poison Control Center at 1-800-222-1222. Get a plant sample because it will aid in diagnosis and treatment. Answer all questions to the best of your knowledge, and follow the advice given by the Poison Control Center or physician. Livestock owners should always provide palatable feed and be especially wary when introducing naïve animals to new pastures. Walk the pasture and look for plants that may be poisonous. In Yavapai County, locoweeds and milkweeds have caused livestock fatalities over the years. In addition, some plants can become toxic in response to environmental conditions (cold temperatures, spring growth, etc.). Your veterinarian can help you learn about local poisonous plant issues. Finally, don’t be paranoid. Just try to build your knowledge of local plant species and whether or not they are toxic. Garden centers, nurseries, florist, and Cooperative Extension can assist in plant identification. Samples for identification should be fresh and include leaves, stem, flowers, and fruit for positive identification. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |