Poison ivy

Botanical Name :  Rhus Toxicodendron
Kingdom: Plantae
Order:     Sapindales
Family: Anacardiaceae
Genus:     Toxicodendron
Species: T. radicans

Synonyms: Poison Oak, Poison Vine, Toxicodendron radicans and Rhus radicans

Common Names : Poison ivy, Eastern Poison Oak

Habitat :  Poison ivy  grows throughout much of North America, including the Canadian Maritime provinces, Quebec, Ontario, Manitoba, and all U.S. states east of the Rocky Mountains, as well as in the mountainous areas of Mexico up to around 1,500 m (4,900 ft) (caquistle or caxuistle is the Nahuatl term ). It is normally found in wooded areas, especially along edge areas where the tree line breaks and allows sunshine to filter through. It also grows in exposed rocky areas, open fields and disturbed areas.

It may grow as a forest understory plant, although it is only somewhat shade tolerant.  The plant is extremely common in suburban and exurban areas of New England, the Mid-Atlantic, and southeastern United States. The similar species T. diversilobum (western poison oak) and T. rydbergii (western poison ivy) are found in western North America.

Rhus Toxicodendron or Toxicodendron radicans rarely grows at altitudes above 1,500 m (4,900 ft), although the altitude limit varies in different locations. 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 be mistaken for tree limbs at first glance.

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

It is more common now than when Europeans first arrived in North America. The development of real estate adjacent to wild, undeveloped land has engendered “edge effects”, enabling poison ivy to form vast, lush colonies in these areas. It is listed as a noxious weed in the US states of Minnesota and Michigan and in the Canadian province of Ontario.

Outside North America,Toxicodendron radicans is also found in the temperate parts of Asia, in Japan, Taiwan, the Russian islands of Sakhalin and the Kuriles, and in parts of China.

A study by researchers at the University of Georgia found that poison ivy is particularly sensitive to CO2 levels, greatly benefiting from higher CO2 in the atmosphere. Poison ivy’s growth and potency has already doubled since the 1960s, and it could double again once CO2 levels reach 560 ppm

Description:
There are numerous subspecies and/or varieties of T. radicans , which can be found growing in any of the following forms, all have woody stems:

* as a trailing vine that is 10–25 centimetres (3.9–9.8 in) tall
* as a shrub up to 1.2 metres (3 ft 11 in) tall
* as a climbing vine that grows on trees or some other support
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The deciduous leaves of T. radicans are trifoliate with three almond-shaped leaflets. Leaf color 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 3–12 cm (1.2–4.7 in) long, rarely up to 30 cm (12 in). 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.[5] 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.

T. radicans spreads either vegetatively or sexually. It 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 (3.1 in) above the leaves. The berry-like fruit, a drupe, mature by August to November with a grayish-white colour. Fruits are a favorite winter food of some birds and other animals. Seeds are spread mainly by animals and remain viable after passing through the digestive tract.

Aids for identification:
The following four characteristics are sufficient to identify poison ivy in most situations: (a) clusters of three leaflets, (b) alternate leaf arrangement, (c) lack of thorns, and (d) each group of three leaflets grows on its own stem, which connects to the main vine.

The appearance of poison ivy can vary greatly between environments, and even within a single area. Identification by experienced people is often made difficult by leaf damage, the plant’s leafless condition during winter, and unusual growth forms due to environmental or genetic factors.

Various mnemonic rhymes describe the characteristic appearance of poison ivy:[8]

1.   “Leaflets three; let it be” is the best known and most useful cautionary rhyme. It applies to poison oak, as well as to poison ivy. Even though it is not always true.

2.   “Hairy vine, no friend of mine. ”

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3.   “Berries white, run in fright” and “Berries white, danger in sight.

Cultivation : 
Succeeds in a well-drained fertile soil in full sun. Judging by the plants natural habitat, it should also succeed in poor acid soils and dry soils. The young growth in spring can be damaged by late frosts. Plants have brittle branches and these can be broken off in strong winds. Plants are also susceptible to coral spot fungus. Plants in this genus are notably resistant to honey fungus. This species is a small suckering shrub, it can spread freely in suitable conditions. There is some confusion over the correct name of this species. It is united with R. radicans (under that name) by some botanists whilst others split this species off into another genus, Toxicodendron, and unite it with R. radicans as Toxicodendron radicans. Many of the species in this genus, including this one, are highly toxic and can also cause severe irritation to the skin of some people, whilst other species are not poisonous. It is relatively simple to distinguish which is which, the poisonous species have axillary panicles and smooth fruits whilst non-poisonous species have compound terminal panicles and fruits covered with acid crimson hairs. The toxic species are sometimes separated into their own genus, Toxicodendron, by some botanists. Dioecious. Male and female plants must be grown if seed is required.
Propagation:
Seed – best sown in a cold frame as soon as it is ripe. Pre-soak the seed for 24 hours in hot water (starting at a temperature of 80 – 90c and allowing it to cool) prior to sowing in order to leach out any germination inhibitors. The stored seed also needs hot water treatment and can be sown in early spring in a cold frame[200]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Cuttings of half-ripe wood, 10cm with a heel, July/August in a frame. Root cuttings 4cm long taken in December and potted up vertically in a greenhouse. Good percentage. Suckers in late autumn to winter.

Edible Uses: Oil.

Medicinal Uses:
Part Used Medicinally: The fresh leaves, from which a fluid extract is prepared.

Constituents: The activity of the drug was formerly ascribed to a fixed oil, Toxicodendrol, but has been attributed more recently to a yellow resin, to which the name Toxicodendrin is applied.

It is Irritant, rubefacient, stimulant, narcotic.

R. Toxicodendron was introduced into England first in 1640, but not used as a medicine till 1798, when Du Fressoy, a physician at Valenciennes, had brought to his notice a young man, who had been cured of a herpetic eruption on his wrist of six years’ standing on being accidentally poisoned by this plant. He thereupon commenced the use of the plant in the treatment of obstinate herpetic eruptions and in palsy, many cases yielding well to the drug. Since then it has rapidly gained a place in general practice, meeting with some success in the treatment of paralysis, acute rheumatism and articular stiffness, and in various forms of chronic and obstinate eruptive diseases.

It is not official in the British Pharmacopoeia, but was formerly official in the United States Pharmacopceia. It is in extensive use by homoeopathists for rheumatism, ringworm and other skin disorders, and is considered by them one of the most useful remedies in a great majority of cases of Nettlerash, especially if caused by some natural predisposition of constitution, in which the eruption is due to the use of some particular food.

The fluid extract, prepared from the fresh leaves, is mostly given in the form of a tincture, in doses of 5 to 30 drops. In small doses it is an excellent sedative to the nervous system, but must be given with care, as internally it may cause gastric intestinal irritation, drowsiness, stupor and delirium.

It has been recommended in cases of incontinence of urine. For this, the bark of the root of R. aromatica is also employed very successfully, an infusion of 1 OZ. to a pint of boiling water being taken in wineglassful doses.

The fluid extract of R. Toxicodendron can be used as a vesicant or blister producer, like cantharides, mezeron, and oil of Mustard.

The best preparation is a concentrated alcoholic tincture made from the green plant in the strength of 1 in 4. The dose of 25 per cent tincture is given in 1 to 5 drops three times a day. A solid extract is not used owing to the extreme volatility of the active principles of the crude drug.

Its milky juice is also used as an indelible ink for marking linen, and as an ingredient of liquid dressings or varnishes for finishing boots or shoes, though R. venenata is more extensively used for the latter purpose.

Other Uses :
Dye; Ink; Mordant; Oil; Parasiticide; Tannin; Varnish.
The leaves are rich in tannin. They can be collected as they fall in the autumn and used as a brown dye or as a mordant. An oil is extracted from the seeds. It attains a tallow-like consistency on standing and is used to make candles. These burn brilliantly, though they emit a pungent smoke. The milky juice makes an excellent indelible marking ink for linen etc. It is also used as a varnish for boots and shoes.

Known Hazards: This plant contains toxic substances and skin contact with it can cause severe irritation to some people. The sap is extremely poisonous. The sap contains 3-N pentadecycatechnol. Many people are exceedingly sensitive to this, it causes a severe spreading dermatitis. The toxins only reach the skin if the plant tissues have been damaged, but even indirect contact can cause severe problems.

Disclaimer:
The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplements, it is always advisable to consult with your own health care provider.

Resources:
http://www.botanical.com/botanical/mgmh/i/ivypoi17.html
http://en.wikipedia.org/wiki/Toxicodendron_radicans

http://www.pfaf.org/user/Plant.aspx?LatinName=Rhus+toxicodendron

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