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=                           Toxicodendron                            =
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                            Introduction
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'Toxicodendron' is a genus of flowering plants in the sumac family,
Anacardiaceae. It contains trees, shrubs and woody vines, including
poison ivy, poison oak, and the lacquer tree. All members of the genus
produce the skin-irritating oil urushiol, which can cause a severe
allergic reaction. The generic name is derived from the Greek words
τοξικόν ('toxikón'), meaning "poison," and δένδρον ('déndron'),
meaning "tree". The best-known members of the genus in North America
are eastern poison ivy '(T. radicans)' and western poison oak ('T.
diversilobum'), both ubiquitous throughout much of their respective
region.

The resins of certain species native to Japan, China and other Asian
countries, such as lacquer tree ('T. vernicifluum') and wax tree ('T.
succedaneum'), are used to make lacquer, and, as a byproduct of
lacquer manufacture, their berries are used to make japan wax.


                            Description
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Plants in the genus have pinnately compound, alternate leaves and
whitish or grayish drupes. They are quite variable in appearance. The
leaves may have smooth, toothed, or lobed edges, and all three types
of leaf edges may be present in a single plant. The plants grow as
creeping vines, climbing vines, shrubs, or, in the case of lacquer
tree ('T. vernicifluum') and poison sumac ('T. vernix)', as trees.
While leaves of poison ivy and poison oaks usually have three
leaflets, sometimes there are five or, occasionally, even seven
leaflets. Leaves of poison sumac have 7-13 leaflets, and of Lacquer
Tree, 7-19 leaflets.


                              Taxonomy
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It was published by Philip Miller in 1754. The lectotype species is
'Toxicodendron pubescens'  The genus is a member of the 'Rhus
complex', and has at various times been categorized as being either
its own genus or a sub-genus of 'Rhus.' There is evidence which points
to keeping 'Toxicodendron' as a separate monophyletic genus, but
researchers have stated that the 'Toxicodendron' and 'Rhus' groups are
complex and require more study to be fully understood.

The common names come from similar appearances to other species that
are not closely related and to the allergic response to the urushiol.
Poison oak is not an oak ('Quercus', family Fagaceae), but this common
name comes from the leaves' resemblance to white oak ('Quercus alba')
leaves, while poison ivy is not an ivy ('Hedera', family Araliaceae),
but has a superficially similar growth form. Technically, the plants
do not contain a poison; they contain a potent allergen.


Species
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29 species are accepted.
* 'Toxicodendron acuminatum'  (synonym 'Rhus acuminata') - China,
Bhutan, India and Nepal.
* 'Toxicodendron bimannii'  - Assam
* 'Toxicodendron borneense'  - Borneo
* 'Toxicodendron calcicola'  - endemic to China
* 'Toxicodendron delavayi'  - southwestern Sichuan and northwestern
and central Yunnan in south-central China
* 'Toxicodendron diversilobum'  (synonym 'Rhus diversiloba') - Western
poison oak is found throughout much of western North America, ranging
from the Pacific coast into the Sierra Nevada and Cascade mountain
ranges between southern British Columbia and southward into Baja
California. It is extremely common in that region, where it is the
predominant species of the genus. Indeed, it is California's most
prevalent woody shrub.  Extremely variable, it grows as a dense shrub
in open sunlight, or as a climbing vine in shaded areas. It propagates
by creeping rhizomes or by seed. The compound leaves are divided into
three leaflets, 35-100 mm long, with scalloped, toothed, or lobed
edges. The leaves may be red, yellow, green, or some combination of
those colors, depending on various factors, such as the time of year.
* 'Toxicodendron fulvum'  - southern Yunnan and northern Thailand
* 'Toxicodendron grandiflorum'  - Yunnan and southwestern Sichuan in
south-central China
* 'Toxicodendron griffithii'  - eastern Himalayas to Yunnan and
southwestern Guizhou in south-central China
* 'Toxicodendron hirtellum'  - southern Sichuan
* 'Toxicodendron hookeri'  - eastern Nepal to Assam
* 'Toxicodendron khasianum'  - Assam and Bangladesh
* 'Toxicodendron × lobadioides'  ('T. diversilobum' × 'T. rydbergii')
- Washington in the northwestern United States
* 'Toxicodendron nodosum'  - western Malesia and southwestern Sulawesi
* 'Toxicodendron oligophyllum'  - Fujian in southeastern China
* 'Toxicodendron orientale'  (synonyms 'Rhus orientale' and 'R.
ambigua') - Asian poison ivy is very similar to the American poison
ivy, and replaces it throughout east Asia (so similar that some texts
treat it as just a variety of the American species).
* 'Toxicodendron pubescens'  (synonym 'Rhus toxicarium')
- Atlantic poison oak grows mostly in sandy soils in eastern
parts of the United States. Growing as a shrub, its leaves are in
groups of three. Leaves are typically rounded or lobed and are densely
haired. Although it is often confused with the more common poison ivy,
even in the scientific literature, Atlantic poison oak has small
clumps of hair on the veins on the underside of the leaves, while
poison ivy does not.
* 'Toxicodendron quinquefoliolatum'  - Guizhou in south-central
China
* 'Toxicodendron radicans'  (synonym 'Rhus radicans') - Poison
ivy is extremely common in some areas of North America. In the United
States, it grows in all states east of the Rockies. It also grows in
Central America. Appearing as a creeping vine, a climbing vine, or a
shrub, it reproduces both by creeping rootstocks and by seeds. The
appearance varies. Leaves, arranged in an alternate pattern, usually
in groups of three, are from 20 to 50 mm long, pointed at the tip, and
can be toothed, smooth, or lobed, but never serrated. Leaves may be
shiny or dull, and the color varies with the season. Vines grow almost
straight up rather than wrapping around their support and can grow to
8-10 m in height. In some cases, Poison ivy may entirely engulf the
supporting structure, and vines may extend outward like limbs so that
it appears to be a Poison ivy "tree".
* 'Toxicodendron rhetsoides'  - Thailand, Laos, and Vietnam
* 'Toxicodendron rostratum'  - southern Yunnan
* 'Toxicodendron rydbergii'  (synonym 'Rhus rydbergii') - Western
poison ivy is found in northern parts of the eastern United States. It
also exists in the western United States and Canada but is much less
common than poison oak. It may grow as a vine or a shrub. It was once
considered a subspecies of poison ivy. It does sometimes hybridize
with the climbing species. Western poison ivy is found in much of
western and central United States and Canada, although not on the West
Coast. In the eastern United States, it is rarely found south of New
England.
* 'Toxicodendron striatum'  (synonym 'Rhus striata') - Manzanillo is a
South American poisonous tree growing in the tropical rain forests on
low elevation slopes. The name should not be confused with the
unrelated Manchineel, a poisonous tree that is not a member of the
Anacardiaceae.
* 'Toxicodendron succedaneum'  (synonym 'Rhus succedanea') - Wax
tree is native of Asia, although it has been planted elsewhere, most
notably in Australia and New Zealand. It is a large shrub or tree, up
to 8 m tall, somewhat similar to a sumac tree. Because of its
beautiful autumn foliage, it has been planted outside of Asia as an
ornamental plant, often by gardeners who were apparently unaware of
the dangers of allergic reactions. It is now officially classified as
a noxious weed in Australia and New Zealand. The fatty-acid methyl
ester of the kernel oil meets all of the major biodiesel requirements
in the USA (ASTM D 6751-02, ASTM PS 121-99), Germany (DIN V 51606) and
European Union (EN 14214).
* 'Toxicodendron sylvestre'  (synonym 'Rhus sylvestris') - native to
China, Japan, Korea and Taiwan.
* 'Toxicodendron trichocarpum'  - southern China, Korea, Japan,
and Kuril Islands
* 'Toxicodendron vernicifluum'  (synonym 'Rhus verniciflua')
- Lacquer tree or varnish tree grows in Asia, especially China
and Japan. Growing up to 20 m tall, its sap produces an extremely
durable lacquer. The leaves have 7-19 leaflets (most often 11-13). The
sap contains the allergenic oil, urushiol. Urushiol gets its name from
this species which in Japanese is called 'Urushi'. Other names for
this species include Japanese lacquer tree, Japanese Varnish Tree, and
Japanese Sumac (Note: the term "varnish tree" is also occasionally
applied to the Candlenut, 'Aleurites moluccana', a southeast Asian
tree unrelated to 'Toxicodendron').
* 'Toxicodendron vernix'  (synonym 'Rhus vernix') - Poison sumac is a
tall shrub or a small tree, from 2-7 m tall. It is found in swampy,
open areas and reproduces by seeds. The leaves have between 7-13
untoothed leaflets, in a feather-compound arrangement. In terms of its
potential to cause urushiol-induced contact dermatitis, poison sumac
is far more virulent than other 'Toxicodendron' species, even more
virulent than poison ivy and poison oak. According to some botanists,
'T. vernix' is the most toxic plant species in the United States
(Frankel, 1991).
* 'Toxicodendron wallichii'  - Himalayas, southern Tibet, southern
China, Vietnam, and northern Thailand
* 'Toxicodendron yunnanense'  - Yunnan


Formerly placed here
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* 'Searsia parviflora'  (as 'Toxicodendron parviflorum' ) -
Small-flowered poison sumac grows in the Himalayas between Kumaun,
India and Bhutan


                                Uses
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In East Asia, in particular in Japan, traditional candle fuel was
produced from 'Toxicodendron vernicifluum' and 'Toxicodendron
succedaneum', among other sumac plants in the genus 'Toxicodendron',
rather than beeswax or animal fats. The sumac wax was a byproduct of
traditional Japanese lacquer manufacture. The conical rousoku candles
produced from sumac wax burn with smokeless flame and were favored in
many respects over candles made from lard or beeswax during the
Tokugawa shogunate. Japan wax is not a true wax but a solid fat that
contains 10-15% palmitin, stearin, and olein with about 1% japanic
acid (1,21-heneicosanedioic acid). It is still used in many tropical
and subtropical countries in the production of wax match sticks.


                             References
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* Frankel, Edward, Ph.D. 1991. 'Poison Ivy, Poison Oak, Poison Sumac
and Their Relatives; Pistachios, Mangoes and Cashews'. The Boxwood
Press. Pacific Grove, Calif. .


                           External links
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*
[https://web.archive.org/web/20030407070238/http://www.pentrace.com/east/wajima/urushi.html
Article about urushi lacquer made from the sap of the Urushi tree of
Japan]
* [http://waynesword.palomar.edu/ww0802.htm Article about poison oak]
*
[https://web.archive.org/web/20070311185409/http://herbarium.uvsc.edu/Virtual/search.asp?s=genus&p=1&n=14915&t=Toxicodendron
UVSC Herbarium - Toxicodendron]
*
* [http://poison-ivy-oak-sumac.com/poison-sumac/ Toxicodendron vernix
(poison sumac) identification]
*


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