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The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 When plants face danger, particularly danger of being eaten, escaping or hiding is not an option. However, plants are not defenceless. Through millennia of evolution, many members of the plant kingdom have invented and mastered an effective defense mechanism – poison, which acts as a deterrent against two-, four- or six-legged herbivores. Some toxic compounds are deadly if ingested, while others can cause only mild discomfort. Among numerous poisonous plants, there are some truly potent killers – the dirty dozen of the plant world. The list opens with the castor bean plant (Ricinus communis). The castor bean contains ricin, one of the most toxic substances known. Deadly ricin is located in seeds that resemble beans and is poisonous unless processed to produce harmless castor oil. If the seed is swallowed with an undamaged seed coat, it will most likely pass harmlessly through the digestive tract. However, if the seed is chewed and swallowed, the ricin toxin will be absorbed within minutes with eventual fatal results. Only one seed is a deadly dose for a child, about four for an adult. Surprisingly, the castor bean plant is commonly grown in the south as a small tree, and in northern countries as a bushy ornamental annual. The deadly castor bean plant is valued for its ornamental properties. White snakeroot (Ageratina altissima) is another infamous member of the dirty dozen. It contains the toxin called tremetol. When eaten by cattle, the cows’ meat and milk become contaminated with the poison, which is passed to humans via consumption. White snakeroot was responsible for thousands of deaths in the 19th century. Poisoning occurred by drinking the milk of cows that had eaten snakeroot. Among the victims, the most famous was Nancy Hanks Lincoln, Abraham Lincoln’s mother. 1/8 www.leevalley.com The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 The next member of the dirty dozen is the well-known yew (Taxus spp.). The entire shrub is poisonous, except for the red flesh of the berries. However, the oval, black seeds within the berries are highly toxic. Fatality can occur within several hours after ingesting as few as three seeds. The primary toxin in yews is taxine, which is a cardiac depressant. Amazingly, this lush, dark green shrub is fairly common in gardens. Every red berry of yew contains one deadly seed. Another silent killer is the oleander (Nerium oleander), the parts of which are all toxic. Just one leaf can kill an adult, and fatal poisonings have resulted from minimal exposure to its twigs, flowers and seed. Even oleander’s nectar and sap have lethal qualities. The plant contains numerous toxins that simultaneously affect the nervous and cardiovascular systems, as well as the digestive tract. However, this evergreen fragrant shrub, valued for its ornamental qualities, is widely cultivated. 2/8 www.leevalley.com The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 As is the case with oleander, all fragments of the rhododendron (Rhododendron spp.) are highly toxic. Even honey produced from rhododendrons is poisonous. Despite these lethal qualities, the plant earns its place as both West Virginia and Washington’s state flower. Rhododendron (and azalea) shrubs offer very showy, occasionally fragrant flower clusters in the spring. Rhododendron ‘Taurus’ usually blooms at the time of the astrological Taurus, sending spectacular, bell-shaped, dark red flowers with maroon flecks. 3/8 www.leevalley.com The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 A close cousin to rhododendrons, mountain laurel (Kalmia latifolia) is a bushy evergreen shrub. The green parts of the plant and its twigs, blooms and pollen are toxic. Honey may produce toxicity symptoms but, fortunately, it is bitter enough to discourage most people from eating it. Symptoms of poisoning appear about six hours following ingestion. The mountain laurel’s very attractive, round flower heads have earned the plant many admirers, as well as a place on Connecticut and Pennsylvania emblems as the state flower. The installations found in Line Garden aim to produce an abstract field. 4/8 www.leevalley.com International Garden Festival Gardening Newsletter Vol. 11, Issue 9 - Septemmber 2016 Some members of the dirty dozen lie low to the ground, such as the innocentlooking lily-of-the-valley (Convallaria majalis). The entire plant, particularly the leaves, is poisonous. Its deadly substance, called convallatoxin, intensifies the heart’s contractions. Lily-of-the-valley is valued as a reliable groundcover in shady, informal settings. Its white, bell-shaped flowers are famous for their potent, sweet scent. Snow-white flowers of the lily-of-the-valley are a symbol of purity, innocence, simplicity and charm. It is hard to believe the deadly potential of this woodland plant. Shown here is the rare variegated lily-of-the-valley (Convallaria majalis) ‘Albostriata’. Another sweetly scented killer is the daffodil (Narcissus spp.). The entire plant has deadly qualities, especially the bulbs, which have potent substances that cause vomiting if ingested. Cases of poisoning have occurred when daffodil bulbs have been mistaken for onions or leeks. However, the unquestionable beauty of daffodils makes them one of the most popular spring flowering bulbs. 5/8 www.leevalley.com The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 Hoop petticoat daffodils (Narcissus bulbocodium) feature grass-like leaves and unusual deep-yellow, trumpetshaped flowers. Their tiny, delicate bodies are full of toxic alkaloids. The statuesque monkshood (Aconitum spp.) is a common garden perennial. All parts of the plant, particularly the tuberous roots and seeds, are extremely poisonous. Ingesting even as little as one gram of the plant may cause death. The plant’s sap is also dangerous, and just slight contact with the flowers can cause fingers to become numb. Don’t be deceived by monkshood’s beauty. The whole plant has poisonous properties. 6/8 www.leevalley.com International Garden Festival Gardening Newsletter Vol. 11, Issue 9 - Septemmber 2016 Monkshood is often confused with another vertical and showy garden plant, the larkspur (Delphinium spp.), which is equally deadly. The entire plant is poisonous, though the young leaves and the mature seeds contain the highest concentration of toxic alkaloids. Six hours is all it takes for delphinium to cause death. This plant is highly valued and commonly grown, anyway. Delphinium is much admired for its beauty when in full bloom but if eaten, it can cause fatal poisoning. Another deadly towering looker is the foxglove (Digitalis purpurea). The entire plant is toxic, especially the leaves of the upper stem, which are full of chemicals that, while used medicinally, are deadly in high doses. Depending on the amount ingested, untreated poisoning leads to death. Foxgloves are still highly regarded as garden plants, since their bell-shaped blossoms growing in tall spires add drama and height. Last but not least of the dirty dozen is the water hemlock (Cicuta maculata), also known as spotted parsley. The whole plant, especially the roots, is poisonous. The poison, called cicutoxin, wastes no time in attacking the central nervous system, and the symptoms are usually very violent. Fortunately, the water hemlock is a wildflower common in the meadow but not in the garden. The poisonous qualities of this plant have long been known. The ancient Greek philosopher Socrates died after drinking a potent solution of water hemlock. It is easy to be deceived by plants. Their beauty, fragrance, and color don’t reveal toxic qualities. Many poisonous plants are common and seemingly innocuous, with their lethal tendencies well-masked. Our gardens and our houses are populated with many green shady characters that we should be aware of, but be particularly wary of the dirty dozen. 7/8 www.leevalley.com The Dirty Dozen Gardening Newsletter Vol. 11, Issue 10 - October 2016 Text and photos by Gina Dobrodzicka Gina Dobrodzicka is a freelance writer and trained horticulturalist living on Vancouver Island. Her website is www.gdgardendesign.com. 8/8 www.leevalley.com