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Poison ivy
Ground-level poison ivy, Ottawa, Ontario
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Sapindales
Family: Anacardiaceae
Genus: Toxicodendron
Species: T. radicans
(L.) Kuntze
Binomial name
Toxicodendron radicans
Synonyms
  • Rhus toxicodendron
  • Rhus radicans

Toxicodendron radicans (Poison ivy; older synonyms Rhus toxicodendron, Rhus radicans[1]) is a plant in the family Anacardiaceae. It is a woody vine that is well known for its ability to produce urushiol, a skin irritant that causes an itching rash for most people, technically known as urushiol-induced contact dermatitis but it is not a true Ivy (Hedera).

Contents

Habitat and range

Poison ivy grows throughout much of North America, including the Canadian Maritime provinces, Quebec and Ontario, and all U.S. states east of the Rockies except North Dakota, as well as in the mountainous areas of Mexico up to around 1,500 m (4,900 ft) (see caquistle or caxuistle—the Nahuatl term), and is normally found in wooded areas, especially along edge areas. It also grows in exposed rocky areas and in open fields and disturbed areas. It also grows as a forest understory plant, although it is only somewhat shade tolerant.[1] The plant is extremely common in suburban and exurban areas of New England, the Mid-Atlantic, and Southeastern United States. Similar species, Poison-Oak, and Toxicodendron rydbergii are found in western North America. Poison ivy rarely grows at altitudes above 1,500 m (4,900 ft), although the altitude limit varies in different locations.[1] The plants can grow as a shrub up to about 1.2 metres (3.9 ft) tall, as a groundcover 10–25 cm (3.9–9.8 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.

It is not particularly sensitive to soil moisture, although it does not grow in desert or arid conditions. It grows in a wide variety of soil types, and soil pH from 6.0 (acidic) to 7.9 (moderately alkaline). It can grow in areas subject to seasonal flooding or brackish water.[1]

It is more common now than when Europeans first entered North America. Real estate development adjacent to wild, undeveloped land has engendered "edge effects," enabling poison ivy to form vast, lush colonies in such places. It is listed as a noxious weed in the U.S. states of Minnesota and Michigan and the Canadian province of Ontario.

Poison ivy and its relatives are virtually unknown in Europe. Many Europeans who hike in the US and Canada are quite surprised to find that such a hazardous plant exists so commonly on the continent.

Description

Poison ivy vine with typical reddish "hairs" (like leaves, vines are extremely poisonous to humans)

The deciduous leaves of poison ivy are trifoliate with three almond-shaped leaflets.[1] Leaf colour ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall; though other sources say leaves are reddish when expanding, turn green through maturity, then back to red, orange, or yellow in the fall. The leaflets of mature leaves are somewhat shiny. The leaflets are 3 to 12 cm long, rarely up to 30 cm. Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth. Leaflet clusters are alternate on the vine, and the plant has no thorns. Vines growing on the trunk of a tree become firmly attached through numerous aerial rootlets.[2] The vines develop adventitious roots, or the plant can spread from rhizomes or root crowns. The milky sap of poison ivy darkens after exposure to the air.

Poison ivy spreads both vegetatively and sexually. Poison ivy is dioecious; flowering occurs from May to July. The yellowish- or greenish-white flowers are typically inconspicuous and are located in clusters up to 8 cm above the leaves. The berry-like fruit, a drupe, mature by August to November with a grayish-white colour.[1] Fruits are a favourite winter food of some birds and other animals. Seeds are spread mainly by animals and remain viable after passing through the digestive tract.

Aids to identification

The following three characteristics are sufficient to identify poison ivy in most situations: (a) clusters of three leaflets, (b) alternate leaf arrangement, and (c) lack of thorns. Although a number of other plants fit this simplified description, any plant with these criteria should be prudently avoided by people unfamiliar with identifying poison ivy. Identification by experienced people is often made difficult by leaf damage, leafless conditions during winter, and unusual growth forms due to environmental and/or genetic factors.

Various mnemonic rhymes describe the characteristic appearance of poison ivy:[3]

  1. "Leaves of three, let it be."
  2. "Hairy vine, no friend of mine."[4] Poison ivy vines are very poisonous.
  3. "Raggy rope, don't be a dope!" Poison ivy vines on trees have a furry "raggy" appearance. This rhyme warns tree climbers to be wary.
  4. "One, two, three? Don't touch me."
  5. "Berries white, run in fright" and "Berries white, danger in sight."[5]
  6. "Longer middle stem, stay away from them." This refers to the middle leaflet having a notably longer stem than the two side leaflets and is a key to differentiating it from the similar-looking Rhus aromatica - Fragrant sumac.
  7. "Red leaflets in the spring, it's a dangerous thing." This refers to the red appearance that new leaflets sometimes have in the spring. (Note that later, in the summer, the leaflets are green, making them more difficult to distinguish from other plants, while in autumn they can be reddish-orange.)
  8. "Side leaflets like mittens, will itch like the dickens." This refers to the appearance of some, but not all, poison ivy leaves, where each of the two side leaflets has a small notch that makes the leaflet look like a mitten with a "thumb." (Note that this rhyme should not be misinterpreted to mean that only the side leaflets will cause itching, since actually all parts of the plant can cause itching.)
  9. "If butterflies land there, don't put your hand there." This refers to the fact that some butterflies land on poison ivy, since they are not affected, which provides them protection as their predators avoid eating the plant.[6]

Effects on the body

The reaction caused by poison ivy, urushiol-induced contact dermatitis, is an allergic reaction. Around 15%[7] to 30%[8] of people have no allergic response, but most people will become sensitized with repeated or more concentrated exposure to urushiol. Reactions can progress to anaphylaxis.

Poison ivy on a roadside

Urushiol binds to the skin on contact, where it causes severe itching that develops into reddish colored inflammation or non-colored bumps, and then blistering. These lesions may be treated with Calamine lotion, Burow's solution compresses or baths to relieve discomfort,[9] though recent studies have shown some traditional medicines to be ineffective.[10][11] Over-the-counter products to ease itching—or simply oatmeal baths and baking soda—are now recommended by dermatologists for the treatment of poison ivy.[12] In severe cases, clear fluids ooze from open blistered sores and corticosteroids are the necessary treatment.

Blisters from contact with poison ivy

The oozing fluids released by itching blisters do not spread the poison.[13][14][15] The appearance of a spreading rash indicates that some areas received more of the poison and reacted sooner than other areas or that contamination is still occurring from contact with objects to which the original poison was spread.[13] The blisters and oozing result from blood vessels that develop gaps and leak fluid through the skin; if the skin is cooled, the vessels constrict and leak less.[citation needed] If poison ivy is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty.[16] If poison ivy is eaten, the digestive tract, airway, kidneys or other organs can be damaged.[citation needed] A poison ivy rash can last anywhere from one to four weeks, depending on severity and treatment. In rare cases, poison ivy reactions may require hospitalization.[13][17]

Urushiol oil can remain active for several years, so handling dead leaves or vines can cause a reaction. In addition, oil transferred from the plant to other objects (such as pet fur) can cause the rash if it comes into contact with the skin.[18][19] Clothing, tools, and other objects that have been exposed to the oil should be washed to prevent further transmission. People who are sensitive to poison ivy can also experience a similar rash from mangoes. Mangoes are in the same family (Anacardiaceae) as poison ivy; the sap of the mango tree and skin of mangoes has a chemical compound similar to urushiol.[20]

Similar reactions have been reported occasionally from contact with the related Fragrant Sumac (Rhus aromatica) or Japanese lacquer tree.

Similar-looking plants

  • Virgin's Bower (Clematis virginiana) (also known as Devil's Darning Needles, Devil's Hair, Love Vine, Traveller's Joy, Virgin's Bower, Virginia Virgin's Bower, Wild Hops, and Woodbine; syn. Clematis virginiana L. var. missouriensis (Rydb.) Palmer & Steyermark [1]) is a vine of the Ranunculaceae family native to the United States. This plant is a vine which can climb up to 10–20 ft tall. It grows on the edges of the woods, moist slopes, fence rows, in thickets and in streambanks. It produces white, fragrant flowers about an inch in diameter between July and September.
  • Box-elder (Acer negundo) saplings have leaves that can look very similar to those of poison ivy, although the symmetry of the plant itself is very different. While box-elders often have five or seven leaflets, three leaflets are also common, especially on smaller saplings. The two can be differentiated by observing the placement of the leaves where the leaf stalk meets the main branch (where the three leaflets are attached). Poison ivy has alternate leaves, which means the three-leaflet leaves alternate along the main branch. The maple (which the box-elder is a type of) has opposite leaves; another leaf stalk directly on the opposite side is characteristic of box-elder.
  • Virginia creeper (Parthenocissus quinquefolia) vines can look like poison ivy. The younger leaves can consist of three leaflets but have a few more serrations along the leaf edge, and the leaf surface is somewhat wrinkled. However, most Virginia creeper leaves have five leaflets. Virginia creeper and poison ivy very often grow together, even on the same tree. Be aware that even those who do not get an allergic reaction to poison ivy may be allergic to the oxalate crystals in Virginia creeper sap.
  • Western Poison-oak (Toxicodendron diversilobum‎) leaflets also come in threes on the end of a stem, but each leaflet is shaped somewhat like an oak leaf. Western Poison-oak only grows in the western United States and Canada, although many people will refer to poison ivy as poison-oak. This is because poison ivy will grow in either the ivy-like form or the brushy oak-like form depending on the moisture and brightness of its environment. The ivy form likes shady areas with only a little sun, tends to climb the trunks of trees, and can spread rapidly along the ground.
  • Poison Sumac (Toxicodendron vernix) has compound leaves with 7–15 leaflets. Poison sumac never has only three leaflets.
  • Kudzu (Pueraria lobata) is a non-toxic edible vine that scrambles extensively over lower vegetation or grows high into trees. Kudzu is an invasive species in the southern United States. Like poison ivy it has three leaflets, but the leaflets are bigger than those of poison ivy and are pubescent underneath with hairy margins.
  • Blackberries and raspberries (Rubus spp.) can resemble poison ivy, with which they may share territory. The chief difference between blackberries and raspberries, on the one hand, and poison ivy, on the other, is that blackberries and raspberries almost always have prickles on the stems, whereas poison ivy is smooth. Also, the three-leaflet pattern of some blackberry and raspberry leaves changes as the plant grows: leaves produced later in the season have five leaflets rather than three. Blackberries and raspberries have many fine teeth along the leaf edge, the top surface of their leaves is very wrinkled where the veins are, and the bottom of the leaves is light minty-greenish white. Poison ivy is all green. The stem of poison ivy is brown and cylindrical, while blackberry and raspberry stems can be green, can be squared in cross-section, and can have prickles. Raspberries and blackberries are never truly vines; that is, they do not attach to trees to support their stems.
  • The thick vines of Riverbank Grape (Vitis riparia), with no rootlets visible, differ from the vines of poison ivy, which have so many rootlets that the stem going up a tree looks furry. Riverbank grape vines are purplish in color, tend to hang away from their support trees, and have shreddy bark; poison ivy vines are brown, attached to their support trees, and do not have shreddy bark.
  • Fragrant Sumac (Rhus aromatica) has a very similar appearance to poison ivy. While both species have three leaflets, the center leaflet of poison ivy is on a long stalk, while the center leaflet of fragrant sumac does not have an obvious stalk. Fragrant sumac produces flowers before the leaves in the spring, while poison ivy produces flowers after the leaves emerge. Flowers and fruits of fragrant sumac are at the end of the stem, but occur along the middle of the stem of poison ivy.

See also

References

  1. ^ a b c d e f USDA Fire Effects Information System: Toxicodendron radicans
  2. ^ Petrides, George A. A Field Guide to Trees and Shrubs (Peterson Field Guides), Boston: Houghton Mifflin Co., 1986, p. 130.
  3. ^ [http://pediatrics.about.com/cs/conditions/a/poison_ivy_3.htm "Poison Ivy Treatment Guide , Getting Rid of the Plants: Identifying Poison Ivy"]. http://pediatrics.about.com/cs/conditions/a/poison_ivy_3.htm. 
  4. ^ http://www.parks.ca.gov/pages/735/files/transcriptmtlivermoreangelisland.pdf Page 3.
  5. ^ Kamp Krusty
  6. ^ Mitchell, Robert. T., "Butterflies and Moths," New York: St. Martin's Press, 2001, p. 133.
  7. ^ Howstuffworks "How Poison Ivy Works"
  8. ^ Contact-Poisonous Plants of the World
  9. ^ Wilson, W. H. & Lowdermilk, P. (2006). Maternal Child Nursing Care (3rd edition). St. Louis: Mosby Elsevier.
  10. ^ "American Topics. An Outdated Notion, That Calamine Lotion". http://www.iht.com/articles/1992/09/09/topi.php. Retrieved 2007-07-19. 
  11. ^ Appel, L.M. Ohmart and R.F. Sterner, Zinc oxide: A new, pink, refractive microform crystal. AMA Arch Dermatol 73 (1956), pp. 316–324. PMID 13301048
  12. ^ "American Academy of Dermatology - Poison Ivy, Oak & Sumac". http://www.aad.org/public/publications/pamphlets/skin_poison.html. 
  13. ^ a b c "Treating Poison Ivy Rash With Home Remedies: Jewelweed;Is Poison Ivy Rash Contagious?". http://landscaping.about.com/cs/weedsdiseases/a/poison_ivy_2.htm. 
  14. ^ "Facts about Poison Ivy: Is it contagious?". http://www.poison-ivy.org/html/faq.htm. 
  15. ^ "Poison Ivy Treatment Guide, Outsmarting Poison Ivy: Treating Poison Ivy Exposures". http://pediatrics.about.com/cs/conditions/a/poison_ivy.htm. Retrieved June 01, 2008. 
  16. ^ "Facts about Poison Ivy: How do you get poison ivy?". http://www.poison-ivy.org/html/faq.htm. 
  17. ^ "Facts about Poison Ivy: How long does the rash last?, What can you do once the itching starts?, How do you get poison ivy?". http://www.poison-ivy.org/html/faq.htm. 
  18. ^ Poison Ivy, Oak & Sumac
  19. ^ "Facts about Poison Ivy: How do you get poison ivy?, Pets and Poison Ivy, How long does the oil last?". http://www.poison-ivy.org/html/faq.htm. 
  20. ^ Mangos and Poison Ivy (New England Journal of Medicine Web Article)

External links


Wikibooks

Up to date as of January 23, 2010
(Redirected to Horticulture/Toxicodendron radicans article)

From Wikibooks, the open-content textbooks collection

< Horticulture
Toxicodendron radicans
Toxicodendron radicans
Toxicodendron radicans

Poison Ivy
Toxicodendron radicans.jpg
Binomial: Toxicodendron radicans
Family: Anacardiaceae

Toxicodendron radicans (syn. Rhus toxicodendron, Rhus radicans; Poison ivy[1]) is a woody vine that is well known for its ability to produce urushiol, a skin irritant that causes an itching rash for most people, technically known as urushiol-induced contact dermatitis.

Poison ivy is subject to frequent taxonomic reclassification and confusion; it is currently divided into eastern and western species in the genus Toxicodendron. At least six distinct subspecies of Toxicodendron radicans are recognized. Complicating identification and taxonomy are the fact that the species (even a particular subspecies) can be highly variable in growth habit and leaf appearance.

It is more common now than when Europeans first entered North America. Real estate development adjacent to wild, undeveloped land has created "edge effects", enabling it to form vast, lush colonies in such places. It is listed as a noxious weed in the U.S. states of Minnesota and Michigan.

Description

The plants can grow as a shrub up to about 1.2 meters (4 ft) tall, as a groundcover 10–25 centimeters (4–10 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.

The leaves are ternate with three almond-shaped leaflets. The berries (actually drupes) are a grayish-white color and are a favorite winter food of some birds. Hence the mnemonic,

"Leaves of three, let it be; berries white, danger in sight."

Another version is:

"Leaves of three let it be; if it's hairy, it's a berry."[2]


The color ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall. The leaflets of mature leaves are somewhat shiny.The leaflets are 3-12 cm long, rarely up to 30 cm. Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth.

Leaflet clusters are alternate on the vine, and the plant has no thorns. These three characteristics: (a) clusters of three leaflets, (b) alternate, and (c) lack of thorns, are sufficient to positively identify the plant. If it is growing up the trunk of a tree, the presence of root-hairs will identify it. [3]

Poison ivy flowers
Box Elder on the left, poison ivy on the right
Poison ivy vine with typical reddish "hairs"

The color ranges from light green (usually the younger leaves) to dark green (mature leaves), turning bright red in fall. The leaflets of mature leaves are somewhat shiny.The leaflets are 3-12 cm long, rarely up to 30 cm. Each leaflet has a few or no teeth along its edge, and the leaf surface is smooth.

Leaflet clusters are alternate on the vine, and the plant has no thorns. These three characteristics: (a) clusters of three leaflets, (b) alternate, and (c) lack of thorns, are sufficient to positively identify the plant. If it is growing up the trunk of a tree, the presence of root-hairs will identify it. [4]

Poison ivy flowers
Box Elder on the left, poison ivy on the right
Poison ivy vine with typical reddish "hairs"

The plants can grow as a shrub up to about 1.2 meters (4 ft) tall, as a groundcover 10–25 centimeters (4–10 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.

The leaves are ternate with three almond-shaped leaflets. The berries (actually drupes) are a grayish-white color and are a favorite winter food of some birds. Hence the mnemonic,

"Leaves of three, let it be; berries white, danger in sight."

Another version is:

"Leaves of three let it be; if it's hairy, it's a berry."[5]

Growing Conditions

It grows throughout much of North America, including all Canadian provinces except Newfoundland (but not the territories) and all U.S. states except Alaska, and is normally found in wooded areas, especially along edge areas. It also grows in exposed rocky areas, in open fields and disturbed areas, and even in areas with wet soils. It rarely grows at altitudes above 1,500 meters (5,000 ft).

Varieties

Aside from the many subspecies, individual plants can vary greatly in the shape of their leaflets.

Confusion with other plants

  • Boxelder (Acer negundo) saplings can look almost indistinguishable from poison ivy. While Boxelder Maples often have five or seven leaflets, three leaflets are also common. The two can be differentiated by the fact that Poison-ivy has alternate leaves, while the maple has opposite leaves; in other words, by observing where the leaf stalk (the "branch" the three leaflets are attached to) meets the main branch. Another leaf stalk directly on the opposite side is characteristic of Boxelder Maple. If the three-leaflet leaves alternate along the main branch, it may be Poison-ivy.
  • Virginia creeper (Parthenocissus quinquefolia) vines can look like poison ivy. The younger leaves can consist of three leaflets (as opposed to the usual five) but have a few more serrations along the leaf edge, and the leaf surface is somewhat wrinkled. The rootlets of a climbing Virginia creeper are paler and much stouter than the hairy roots of poison ivy, which are dark red. Virginia creeper and poison ivy grown in the same habitat and frequently co-occur, often on the same trees.
  • Poison Sumac (Toxicodendron vernix) has compound leaves with 7–15 leaflets. Poison sumac never has only three leaflets.
  • Kudzu (Pueraria lobata) is a non-toxic edible vine that scrambles extensively over lower vegetation or grows high into trees. Kudzu is an invasive species in the southern United States. Like poison ivy it has three leaflets, but the leaflets are bigger than those of poison ivy and are pubescent underneath with hairy margins.
  • Blackberry and raspberry vines bear a passing resemblance to poison ivy, with which may share territory. The chief difference between blackberry vines and poison ivy is that blackberry vines have spines on them, whereas poison ivy is smooth. Also, the three-leaflet pattern of blackberry vine leaves changes as the plant grows: the two bottom leaves both split into two leaves, for a total of five in a cluster. They have many teeth along the leaf edge, and the top surface of their leaves is very wrinkled where the veins are, and the bottom of the leaves is light minty - greenish white, while poison ivy is all green. The stem and vine of poison ivy are brown and woody, while blackberry stems are green with thorns.

Toxic effects

See Urushiol-induced contact dermatitis for more details about the rash, including prevention and treatment.

The reaction caused by poison-ivy, urushiol-induced contact dermatitis, is an allergic reaction. Around 15%[6] to 30%[7] of people have no allergic response, but most if not all will become sensitized over time with repeated or more concentrated exposure to urushiol.

For those who are affected by urushiol, it causes a very irritating rash. In extreme cases, corticosteroids can be needed to treat rashes and severe itching. The first symptom of contact is a severe itching of the skin that develops into reddish colored inflammation or non-colored bumps, and then blistering of the skin occurs. In severe cases, clear fluids ooze from open blistered sores. The urushiol poison is quickly bound to the skin after contact.

The oozing fluids released by itching blisters do not spread the poison. The appearance of a spreading rash indicates that some areas received more of the poison and reacted sooner than other areas. The blisters and oozing result from blood vessels that develop gaps and leak fluid through the skin; if the skin is cooled, the vessels constrict and leak less. If poison ivy is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty. If poison ivy is eaten, the digestive tract, airway, kidneys or other organs can be damaged.

Understanding why new lesions may develop for two weeks (studied on forearm) after one exposure was made clear by a Univ of Miami scientist: larger amounts have earliest onset and largest reaction, smallest produce a delayed reaction. The overall severity 'progresses' with the combined active lesions. Therefore, the last new lesion should occur at two weeks after last exposure, the total rash (untreated) may go on for 3-4 weeks.

Urushiol oil can remain active for several years, so handling dead leaves or vines can cause a reaction. In addition, oil transferred from the plant to other objects (such as pet fur) can cause the rash if it comes into contact with the skin.[8]

People who are sensitive to poison-ivy can also experience a similar rash from mangoes; the skin of mangoes has a chemical compound similar to urushiol. [9] Similar reactions have been reported occasionally from contact with the related aromatic sumac or Japanese lacquer tree.

Maintenance

Control

Pests and Diseases

References

  1. USDA Fire Effects Information System: Toxicodendron radicans
  2. http://www.parks.ca.gov/pages/735/files/transcriptmtlivermoreangelisland.pdf Page 3.
  3. Petrides, George A. A Field Guide to Trees and Shrubs (Peterson Field Guides), Boston: Houghton Mifflin Co., 1986, p. 130.
  4. Petrides, George A. A Field Guide to Trees and Shrubs (Peterson Field Guides), Boston: Houghton Mifflin Co., 1986, p. 130.
  5. http://www.parks.ca.gov/pages/735/files/transcriptmtlivermoreangelisland.pdf Page 3.
  6. http://science.howstuffworks.com/poison-ivy.htm
  7. http://mic-ro.com/plants/
  8. http://www.aad.org/public/Publications/pamphlets/Poison_IvyOakSumac.htm
  9. Mangos and Poison Ivy (New England Journal of Medicine Web Article)
Wikiversity
Wikiversity is collecting bloom time data for Toxicodendron radicans on the Bloom Clock








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