Hemlock is a famous poisonous plant that blooms freely in open fields and ditches alongside Queen Anne’s Lace and Black Eyed Susans. Hemlock looks like a carrot when it is young and resembles wild carrot when it flowers.
Common Vetch, a small vine with purple flowers, is toxic, as is Bleeding Heart, a popular shade garden plant.
Many grasses can become poisonous if they are infected with the deadly fungus ergot. Ryegrass is especially vulnerable.
Jack in the Pulpit, Green Dragon and other members of the Arisaema or Arum family are also entirely toxic. The corms, leaves, stems and flowers contain bundles of calcium oxalate that pierce mouth and throat tissue. Skunk cabbage is another member of that family to avoid.
Jimsonweed or Datura, sacred thorn-apple,
is grown for its beautiful flowers and grows in the wild. All parts of the plant and all of its relatives in the Brugmansia family contain indole alkaloids that affect the nervous system. The symptoms resemble belladonna poisoning.
Mayapple, in the barberry family, is a highly prized spring flowering woodland perennial. The entire plant with the exception of its ripe berries can be fatal if eaten. It has 15 active poisonous compounds.
Milkweeds poison livestock and humans if eaten raw. The toxicity is low but the milky juice that the stems contain can cause a rash on sensitive skin.
Pokeweed is a beautiful wild plant with purple-black berries that are loved by birds.
The entire plant is poisonous, including leaves, roots, stems and seeds. People who enjoy eating pokeweed in the spring boil the young leaves in 4 changes of water to remove the toxins.
St. Johnswort plants contain a phototoxin that causes inflammation. It is commonly used as a medicinal herb to calm the nerves and ease depression.
Cherry Laurel, a small tree or hedgerow plant produces poisonous flowers, fruits, leaves and seed kernels. Its relative, Carolina laurelcherry is also toxic.
Yew is an evergreen tree or shrub with red berry-like fruit. The needles contain a poison that causes severe abdominal illness.
Box or boxwood shrubs are very common landscape plants. All parts of boxwood contain steroidal alkaloids which are poisonous.
Pieris japonica is a shrub with leathery leaves and white or pink flowers. The leaves are toxic if eaten. Symptoms include prickly skin, headache, weakness and slow heartbeat.
Rhododendrons and azaleas are shade loving shrubs that flower in the spring. The leaves, flowers, pollen and nectar poison bees as well as the honey they produce from the flowers.
Clematis is a flowering perennial woody vine. Many plants in the buttercup family, including Clematis contain protoanemonin in the leaves and sap. It causes skin blistering in some people. Eating the leaves causes inflammation of the mouth and digestive tract.
Morning glory is a flowering vine that returns from seed. The seeds contain amides of lysergic acid. Symptoms include nausea and hallucinations.
Wisteria is a vigorous woody vine with purplish flowers in the spring. The entire plant is toxic. Eating 2 seeds can cause serious illness.
Children and pets put just about everything into their mouths so keep an eye on them when visiting gardens and parks.
Concerns? Contact the American Association of Poison Control Centers (www.aapcc.org and http://oklahomapoison.org) 24 hours a day, 7 days a week at 800-222-1222.
An online chart of common poisonous plants is at Texas State Department of Health at http://aggie-horticulture.tamu.edu/lawn_garden/poison/poison.html.
A good reference to have around is, “The North American Guide to Common Poisonous Plants and Mushrooms” by Nancy Turner and Patrick von Aderkas.