Poisonous plants

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Some poisonous plants of Tennessee

About this page
This page is designed to present some general information about poisonous plants that may be commonly found in the southeastern U.S. It is not intended to be comprehensive or authoritative. Never eat any part of any plant unless you are confident of your identification and of your knowledge that the part of the plant is safe to eat!!!

For more authoritative information and treatment advice, contact the Tennessee Poison Center at 1-800-222-1222

Quick links: Don't touch Notorious poisons Precautions Edible plants Herbal remedies

Plants that are "poisonous" to the touch

There are several plants that are irritating to the touch or which cause an allergic reaction for many people. Although annoying, these plants are native and an important part of the natural ecosystem in southeastern forests.

Poison ivy (Toxicodendron radicans) The most common and well-known irritating plant in this area is poison ivy. It can grow as a groundcover or as a "hairy" vine climbing up the bark of trees. Skin contact with the any part of the plant can result in an allergic response that causes itching red spots and blistering. Washing thoroughly with warm soapy water can reduce the likeliness of a reaction if you have touched the plant. Poison oak is a similar species with the same effects.

The three, toothed leaflets of poison ivy may be confused with box elder (Acer negundo). However, box elder is a freestanding tree and has leaves that are opposite on the stem rather than alternate like poison ivy.

Nettles (left: woodnettle Laportea canadensis, center and right: stinging nettle Urtica chamaedryoides) have stinging hairs on their stems and leaves which can produce a short-lived stinging or burning sensation when brushed against.

Notoriously poisonous plant families

Apiaceae ("umbellifers", the carrot family)

Despite the presence of celery and carrots in this family, many members of the family are highly poisonous.

Poison hemlock (Conium maculatum) is probably the most famous poisonous member of this family. Although not native to the United States, it has become established here and is a fairly common roadside weed. This particular plant was growing along the road near my home in middle Tennessee. It can grow up to 3 meters (10 feet) tall and is easily recognized by the purple splotches on its stem. Contact with this plant can cause dermatitis, so wear gloves when pulling it.

The plants fame comes from its use in the execution of the famous Greek philosopher, Socrates, who was made to drink an extract from the plant. Poison hemlock should not be confused with the tree, eastern hemlock (Tsuga canadensis) which is relatively harmless. Eastern hemlock is a dominant tree in the Smoky Mountains and is sometimes planted as an ornamental.

Solanaceae (nightshade family)

Again it is ironic that several important foods (tomatoes, peppers, and potatoes) are members of this otherwise deadly family. Its most famous member, deadly nightshade or belladonna (Atropa bella-donna) is native to Europe and isn't normally found in Tennessee. However, there are other common poisonous representatives in this area.

Horse nettle (Solanum carolinense) is a common native roadside weed that is found throughout most of the U.S. I photographed this flower by my mailbox. It is pretty easy to recognize when in its white or purple flowers are visible. It is also notable for its spiny stems and the spines on the bottom of the leaves. The yellow berries could be mistaken for an unripe cherry tomato and cause severe poisoning. The plant may irritate your skin, especially if the skin is scratched by the prickles.

Jimson weed (Datura stramonium) is a common pest weed in agricultural areas, roadsides, and waste places. It is easy to recognize and the fruits (which look like a medieval weapon) are unmistakable. People are regularly poisoned by eating its seeds.

Some general points about poisonous plants:

There are many other poisonous plants that grow wild in the southeastern U.S. You can learn to recognize many of them with a good field guide, such as Wildflowers of Tennessee (Jack Carman, 2001). You can be concerned about the safety of yourself and your children and still have a great time enjoying plants in the outdoors if you remember a few main points:

	Do not let your children put any part of any plant in their mouth without your permission. There are several species of plants that are sweet or sour and therefore fun for children to taste. But make sure that you can correctly identify them before you let your children taste them.
	Plant parts that are edible when young or properly prepared may be poisonous when older or improperly cooked. There is a long tradition in the south of gathering and eating wild greens such as cress and mustard greens. In some cases, boiling in several changes of water to remove hazardous compounds is necessary before wild greens and some kinds of nuts can be eaten. Learn from a knowledgeable person before you eat wild plants that you collect yourself.
	One part of a plant may be edible, while other parts may be poisonous. Rhubarb, which has edible stems and poisonous leaves is a common example. The poisonous berries of pokeweed are another. Again, consult with someone who has experience preparing the plant before you try it yourself.
	Plant compounds that are drugs are usually poisons at higher doses. Many important therapeutic drugs (for example, digitalis from the foxglove plant) are extracted from plants, while the plants themselves are poisonous. Never eat or smoke plant parts that you collect in an attempt to "get high". That can put you at great risk from poisoning.
	Teach your children to recognize poison ivy.
	Leave mushroom collecting to experts. Mushrooms are actually fungi and not plants, but since they are commonly collected to eat, they will be mentioned here. Even a tiny bite of some poisonous mushrooms can be fatal. So unless you have been carefully trained by an expert to recognize edible mushrooms, buy your mushrooms at the grocery store!

What wild plant parts can I safely eat?

Common berries such as blackberries, raspberries, blueberries, and mulberries are fairly easy to recognize and many are very tasty. But make sure that you know how to identify them before you eat them. All of these berries are generally found on woody trees or shrubs, and many are black or dark blue when ripe.

What about herbal remedies and supplements?

Many of the important drugs we use today can trace their origin to herbal remedies of the past. So obviously, some herbal remedies may have medicinal value. However, herbal remedies are not required to undergo stringent testing like therapeutic drugs, which must be shown to be safe and effective before they can be marketed.

It is a misconception that things that are "natural" are more safe to use. Some of the most deadly poisons known to humans come from natural sources, including plants.

Before taking any herbal remedies, do careful research into the known risks associated with the herb. Ask your doctor whether taking it may introduce complications related to conditions that you may have or cause harmful interactions with drugs that you are taking.

Written by Steve Baskauf, Ph.D., August 2006