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Poison sumac
Poison sumac leaves

Secure  ( NatureServe) [2]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Anacardiaceae
Genus: Toxicodendron
T. vernix
Binomial name
Toxicodendron vernix
Synonyms [3]
    • Rhus aequalis Pers.
    • Rhus venenata DC.
    • Rhus vernix L.

Toxicodendron vernix, commonly known as poison sumac, [4] or swamp-sumach, [5] is a woody shrub or small tree growing to 9 metres (30 feet) tall. [6] [7] It was previously known as Rhus vernix. This plant is also known as thunderwood, particularly where it occurs in the southern United States.

All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans. Urushiol is the same chemical that poison ivy is covered in. 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.


Poison sumac is a shrub or small tree, growing up to nearly 9 metres (30 feet) in height. Each pinnate leaf has 7–13 leaflets, each of which is 5–10 centimetres (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) 8–20 cm (3–8 in) long. The fruits are subglobose (not quite spherical), whitish-gray, flattened, and about 0.5 cm (14 in) across; these are eaten by birds. [8]

Poison sumac fruit are creamy white and part of a cluster. Typically, they are around 4 to 5 millimetres (532 to 316 in) in size.

Poison sumac

Distribution and habitat

Poison sumac grows exclusively in wet and clay soils, usually in swamps and peat bogs, in the eastern United States and extreme southeast Canada. [4]


The fruit and leaves of the poison sumac plant contain urushiol, an oil that causes an allergic rash upon contact with skin. They are, however, not toxic to birds or other animals, and eaten by them when other food is scarce, especially in winter. [9]


In terms of its potential to cause urushiol-induced contact dermatitis, poison sumac is more toxic than its relatives poison ivy and poison oak.

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. [6] In the worst case, smoke inhaled by burning poison sumac leads to life-threatening pulmonary edema whereby fluid enters the alveoli. [10]

Poison sumac at Cedarburg Bog State Natural Area in Ozaukee County, Wisconsin

See also


  1. ^ Maiz-Tome, L. (2016). "Toxicodendron vernix". IUCN Red List of Threatened Species. 2016: e.T64325354A67731112. doi: 10.2305/IUCN.UK.2016-1.RLTS.T64325354A67731112.en. Retrieved 19 November 2021.
  2. ^ "NatureServe Explorer 2.0". Retrieved 26 October 2022.
  3. ^ "Toxicodendron vernix (L.) Kuntze". Plants of the World Online. Board of Trustees of the Royal Botanic Gardens, Kew. 2017. Retrieved 27 September 2020.
  4. ^ a b USDA, NRCS (n.d.). "Toxicodendron vernix". The PLANTS Database ( Greensboro, North Carolina: National Plant Data Team. Retrieved 12 December 2015.
  5. ^ Kalm, Pehr (1772). Travels into North America: containing its natural history, and a circumstantial account of its plantations and agriculture in general, with the civil, ecclesiastical and commercial state of the country, the manners of the inhabitants, and several curious and important remarks on various subjects. Translated by Johann Reinhold Forster. London: T. Lowndes. p.  60. ISBN  9780665515002. OCLC  1083889360.
  6. ^ a b Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scribner's Sons. pp. 94–96.
  7. ^ Rucker, Colby. "Tall Trees of Maryland". Maryland's Tallest Native Tree Species. Retrieved 20 January 2012.
  8. ^ Niering, William A.; Olmstead, Nancy C. (1985) [1979]. The Audubon Society Field Guide to North American Wildflowers, Eastern Region. Knopf. p. 327. ISBN  0-394-50432-1.
  9. ^ Little, Elbert L. (1980). The Audubon Society Field Guide to North American Trees: Eastern Region. New York: Knopf. p. 553. ISBN  0-394-50760-6.
  10. ^ "Poison Sumac". The Poison Ivy, Poison Oak, Poison Sumac Site.

Further reading

External links