Poison Ivy is a toxic plant that many campers, cottagers and rural gardeners are familiar with. I myself have been a victim of its rash and blisters and have become quite familiar with those leaflets three and so I do let them be. Only when I began to research Poison Ivy did I realize how little I did know and how far back people have been dealing with the consequences of coming in contact with this plant.
History of Poison Ivy
Originally rumored to have come from Europe, Poison Ivy has been in Americas for centuries. In fact, it was even documented as being observed first hand in Bermuda and the Americas by Captain John Smith in his publication Generall Histories of Virginia, New England and the Summer Isles written in 1624. “The poysoned weed is much in shape like our English Ivy, but being but touched, causeth rednesse, itching, and lastly blisters, the which howsoever after a while passe away of themselves without further harme, yet because for the time they are somewhat painfull, it hath got itselfe an ill name, although questionlesse of no ill nature.”
Even in the 1784 First Volume called Memoirs of the American Society of Arts and Science mentioned a plant that “produced inflammations and eruptions”. They then went on to nickname the plant as “poison Ivy”. Since then there have been countless articles, research and trials attempting to control the spread of this toxic plant.
Poison Ivy Plant Classification
Poison Ivy as we know it to be called is really just one of many poisonous plants in the family of Anacardiaceae. In fact the cashew tree whose name forms the basis of this family does have toxic resins in the casing that surrounds the nut itself.
The English word for this family is derived from two Portuguese words which describe how the cashew nut grows… “ana” which means upward and “cardium” which means heart. Originally native to Northern Brazil, the Cashew was taken by the Portuguese to Goa in India around the year 1560-65 and now they are grown in parts of Africa and throughout Southeast Asia.
The cashew nut is really a seed, whose casing, called a cashew apple, contains skin irritating chemicals, one of which is related to the oil; Urishiol found in poison ivy. In fact, roasting does destroy the compound, but just as with poison ivy, the smoke contains the chemical and inhalation causes severe lung irritations.
Interestingly enough the mango, which is in the same family, has an urushiol oil based allergen that can also cause dermatitis and even anaphylaxis in in some people. The urushiol is present in the mango leaves, stems, skin and sap. Eating unripe, pickled or cooked fruit, the skin of the mango is edible but susceptible people may still get dermatitis of the lips, or the tongue. Generally ripe mangos should be peeled before consumption to avoid the oils. Despite this, further research has provided data stating the during the mango primary ripening season, it is the most common source of plant dermatitis in Hawaii.
Originally Poison Ivy was known as Rhus radicans; part of a the genus Rhus which contains over 250 species of flowering plants including all varieties of sumacs, poison ivy, and poison oak. Research data has suggested that the Genus be split in to 6, based on redefined plant characteristics. In this case there would be only approximately 35 plants left in the Rhus genus.
Created from further botanical clarification, botanists generally accept the reclassification of Poison Oak, Poison Sumac and Poison Ivy in to the genus Toxicodendron, which is Greek for two words, meaning toxic and tree. All three of these plants contain some version of chemical compounds called pentadecylcatechols or PDC’s. Found in the clear sap of these three plants as well as other members of the Anacardiaceae or Cashew family worldwide, the PDC’s are generally referred to as urushiol.
This term was taken from the Japanese name for a tree there called Toxicodendron vernicifluum. Despite the toxic chemicals there, the Japanese have used an oxidized form of the tree sap, to produce its famous finish for their lacquer ware.
Poison Ivy Range
This particular toxic plant ranges from Canada to the north down through the United States, areas of Mexico and in to South America. Poison Ivy may be found in these countries up to approximately 1,500 M (4,900 ft) but is extremely common along the edges of wooded areas, in open fields and other undisturbed areas.
While it is recognized as a creeping plant, it also grows bush like. Regardless of the style of growth, poison ivy is considered officially a noxious weed here in Ontario Canada and in the U.S. states of Minnesota and Michigan. Although some varieties are shade tolerant, all forms of this poison plant prefer sun and in fact Poison Ivy was recently located at my favourite beach!
Beach-side Poison Ivy warning sign
Poison Ivy Forms
Basking in the sun, this shrub form is merely one of the three ways this plant can be found. In fact, the shrub can grow one main stem with side branches, up to over 1 metre (3 ft) tall. Certainly as it is called ivy, given a good support pole, plant or tree, poison Ivy can grow taller than you can imagine. A good example, (Or bad) is the large mass of vines attached to a pine trees at my cottage by hair like brown aerial roots to a height of over 25metres (80 Feet). The last form is as a groundcover of 10-25 cm (4-10inches), as often seen in campgrounds and growing between other native plants along roadsides.
Trillium and poison ivy roadside
The vine and bush plants have a rhizome root base. This allows the roots and new plants to spread from the subterranean nodes. The aerial roots attach themselves to the plant / object for support and nutrition.
Poison Ivy root runner
Poison Ivy stems are woody and grey. On small plants the colour may not be as noticeable, but is definitely seen on bush and trees climbing forms. In fact, the wood on the vines of poison ivy that are climbing up the pine trees at my cottage have a dark grey to reddish tint. Their hair- like roots, which are reddish in colour are also poisonous to humans.
Despite knowing the old saying” leaflets three, let it be”, there are other plants with similar three leaf configuration. Generally there is one leaf and the end and two below that which are side by side. They are normally 10-20 cm (2-4inches) in length, with toothed or lobed edges, although occasionally the edges can be smooth.
Of course when they are small, but still containing urushiol, they begin with two leaves only, so weeding in the front of a rural garden especially can be dangerous if gloves are not worn. In the spring, the new leaves are a reddish green colour, changing to deep green and then yellow, orange and red in the fall before dropping off.
Despite having poison ivy in various locations at my cottage, I had not seen the flowers myself until recently when visiting my favourite beach. In full sun the shrub form had developed 2.5 to 7.5 cm (1-3inch) clusters of the small green flowers. The tiny 5 petal blooms are quite often hidden under the leaves themselves.
Poison Ivy flower
Small flowers produce small seeds and these tiny white berries are round, hard and about 0.4 cm (1/8inch) that have ridges in them that make them appear to have segments like a peeled orange. Forming in the fall, the berries contain the seeds of the plant which are spread by the over 50 species of birds that eat them with no ill effects.
Poison Ivy Berries/seeds
It is estimated that 85% of the population is sensitive to the urushiol toxin found in all parts of the poison ivy plant. Skin reactions range from a slight dermatitis called Rhus dermatitis, to blisters. These blisters result from blood vessels somehow developing gaps in response to the chemical in the oil and then fluid leaks through in to the skin. The blister themselves do not contain the urushiol. In severe cases these blister cause tissue damage and may need plastic surgery to repair. In extreme situations, anaphylaxis may occur.
If you believe you have bruised the plant and released the oil, wash the affected area immediately with soap and water. Rubbing alcohol will also remove the oil and now specific lotions are available at the drugstore. According to recent testing, there is a compound in crushed Jewelweed (Impatiens capensis) that relieve the effects of recent contact with poison ivy in about 85% of people tested. Dermatologists recommend oatmeal baths and baking soda to relieve the itching and there are prescription cortisol based lotions for more severe cases.
Remember that all clothing and even tools need to washed down well in the same way, because the oil remains potent indefinitely and it will re-poison you. Further risk comes from transfer by other animals and even of burning the plant. Dogs for example have some resistance due to their thick fur and the natural oils there, but can transfer it to their owners’ hands. Smoke from burning any and all parts of this plant contain the oils and can cause serious allergic reactions inside lungs of susceptible people.
Controlling Poison Ivy is a challenge regardless of the affected area, because of its toxic oils. As a result, the number one thing to remember is to wear protective clothing. Cloth or leather gardening gloves are recommended over rubber as according to several sources, the urushiol is soluble in rubber. Even in the garden at the cottage I wear gloves as …surprise…poison ivy alert under the perennials!
Poison Ivy in my garden
If the poison ivy is a few plants, growing as ground cover, then carefully pulling them out with all the roots works. Then the plant needs to be discarded safely. I have a large plastic pail with a lid, and the smaller pieces go in there to die completely. After a month, once there is no sign of life, I dig a hole about one foot deep and bury them.
When poison ivy is growing on a larger scale, the task of control definitely becomes difficult. One suggestion for large mass plants is covering them over with tarps and soil so no light reaches these and they will die. Of course they need to remain covered for several years before it is safe to assume they are dead.
Shrub forms of poison ivy are very difficult to deal with. If the shrub is not too large, herbicide spray can be used. The newest generation of these sprays interfere in the plants photosynthesis when the leaves are saturated. It is important to wear protective gloves , face shield and disposable gloves when using these products.
Controlling Poison Ivy is possible, however, even using herbicides that do not leach in to the soil, getting rid of it for good is highly unlikely. In addition, beware of home remedies that are dangerous, such as pouring salt or bleach all over them because the soil is then contaminated and the chemicals can leach in to the water table.
While contact with poison ivy can have toxic consequences, by wearing gloves in the rural gardens and watching vegetation you are walking through carefully you can minimize your risk. If you live in the country and have dogs, the chances are much higher you may contact it from their coats. In that case, having a knowledge of treatment including rubbing alcohol and lotions would be a good precaution.