Rhus vernix

Systematik

Toxicodendron vernix, commonly known as poison sumac, is a woody shrub or small tree growing to 9 m (30 ft) tall. It was previously known as Rhus vernix. This plant is also known as thunderwood, particularly where it occurs in the southern US states. All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans. When the plant is burned, inhalation of the smoke may cause the rash to appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty.

Description

Poison sumac is a shrub or small tree, growing up to nearly 30 feet in height. Each pinnate leaf has 7–13 leaflets, each of which is 2–4 inches long. These are oval-to-oblong; acuminate (tapering to a sharp point); cuneate (wedge-shaped) at the base; undulate (wavy-edged); with an underside that is glabrous (hairless) or slightly pubescent (down-like hair) beneath. The stems along the leaflets are red and the leaves can have a reddish tint to them, particularly at the top of the plant. New bark for a poison sumac tree is lightish gray, and as the bark ages, it becomes darker.

Its flowers are greenish, growing in loose axillary panicles (clusters) 3–8 inches long. The fruits are subglobose (not quite spherical), gray, flattened, and about 0.2 inches across.

Poison sumac fruit are creamy white and part of a cluster. Typically, they are around 4 to 5 mm (0.18 inches) in size.

The fruit and leaves of the poison sumac plant contain urushiol, an oil that causes an allergic rash upon contact with skin.

Poison sumac

Distribution

Poison sumac grows exclusively in wet and clay soils, usually in swamps and peat bogs, in the eastern United States and extreme southeast Canada.

Toxicity

In terms of its potential to cause urushiol-induced contact dermatitis, poison sumac is more toxic than its relatives poison ivy and poison oak. According to some botanists, poison sumac is the most toxic plant species in the United States (Frankel, 1991).

The differences in toxicity in poison ivy, poison oak, and poison sumac are due to differences in the side chains of the chemicals in these plants. In general, poison ivy has a C₁₅ side chain, poison oak has a C₁₇ side chain and poison sumac has a C₁₃ side chain.

The dermatitis shows itself in painful and long continued swellings and eruptions. In the worst case, smoke inhaled by burning poison sumac leads to a life-threatening medical condition pulmonary edema whereby fluid enters the alveoli.

References

• Frankel, Edward, Ph.D. 1991. Poison Ivy, Poison Oak, Poison Sumac and Their Relatives; Pistachios, Mangoes and Cashews. The Boxwood Press. Pacific Grove, Calif. ISBN 0-940168-18-9.
• http://www.forestry.state.al.us/Publications/TREASURED_Forest_Magazine/2008%20Spring/Trees%20of%20Alabama%20-%20Poison%20Sumac.pdf.

External links

• Poison ivy / oak / sumac in "The Medicinal Herb FAQ".
• The Poison Sumac Page—Photos and facts about poison sumac.
• Poison Oak at Wayne's Word.

Further reading

• Aaron Gladman: Toxicodendron Dermatitis: Poison Ivy, Oak, and Sumac. In: Wilderness & Environmental Medicine. 17. Jahrgang, Nr. 2, Juni 2006, S. 120–128, doi:10.1580/PR31-05.1, PMID 16805148. 
• Jere Guin, William Gillis, John Beaman: Recognizing the Toxicodendrons (poison ivy, poison oak, and poison sumac). In: Journal of the American Academy of Dermatology. 4. Jahrgang, Nr. 1, Januar 1981, S. 99–114, doi:10.1016/S0190-9622(81)70014-8 (sciencedirect.com [abgerufen am 1. Mai 2015]). 
• William L. Epstein: The Poison Ivy Picker of Pennypack Park: The Continuing Saga of Poison Ivy. In: Journal of Investigative Dermatology. 88. Jahrgang, 3 Suppl, März 1987, S. 7s-11s, doi:10.1111/1523-1747.ep12468865.