Friday, November 4, 2011

Leaves Of Three, Let It Be - Toxicodendron radicans - Poison Ivy

Toxicodendron radicans - Poison Ivy, also know as Rhus radicans or Rhus toxicodendron, is a poisonous North American plant that is well known for its production of urushiol, a clear liquid compound found within the sap of the plant that causes an itching rash in most people who touch it.  The plant is not a true ivy (Hedera).

Toxicodendron is from the Latin toxicum, 'poison', and the Greek dendron, 'tree'; hence "poison tree". Rhus may come from the Greek reo, meaning 'to flow' indicating the spreading nature of the plant. Radicans is from the Latin for radiating, thus a plant with radiating stems which will form additional roots.

The leaves are alternate and compound, with three pointed leaflets; the middle leaflet has a much longer stem than the two side ones, often the two side leaflets appear stem-less.  The stems will sometimes appear to be 'hairy,' but not always.  Sometimes there will be only a few rootlets appearing on the stems.

The leaflet edges can be smooth, toothed or sometimes lobed, they can vary from stiff and leathery to thin, and from hairy beneath to no hairs at all.  The leaves vary greatly in size, from 0.31" to 2.16" in length.  They are sometimes reddish and glossy when they emerge in the spring, turn a dull green during the summer, and become various shades of yellow, orange or red in the autumn. 

 Flowers are yellowish to greenish in color and grow in small branching clusters in the axils (where the leaf stem joins the main branch).  The flowers are approximately 1/8 inch in diameter, and bloom from May through July.  They are whitish, with a waxy look. Poison ivy fruit matures from August through October.  They form in a cluster of smooth, round berries of approximately 3/16 inch in diameter. They are pale green to grayish white in color with a waxy look.

There are a lot of myths about Poison Ivy, and I hope to dispel most of those for you. So, here are some good solid facts to help if you should ever come into contact with it.
  • The plant produces Urushiol oil, which is responsible for the rash. Although some people may seem to be immune, 90% of people in the USA are allergic to urushiol oil. Sensitivity to urushiol can develop at any time, the more you are exposed to it, the more likely you will develope an allergic rash. It's just a matter of time.
  • For the first time sufferer, it takes longer for rash to show up, usually in 7 to 10 days.
  • Direct contact is needed to release urushiol oil. However, fire and machinery can cause the oil to become airborne, so stay away from forest fires, direct burning, lawnmowers, and trimmers.
  • Urushiol oil stays active on any surface, including dead plants, for up to 5 years.
  • Solutions or cures for the rash are those that annihilate the urushiol oil.
  • Breaking the blisters does not release and spread urushiol oil, but your wounds can become infected and you may make the scarring worse. In very extreme cases, excessive fluid may need to be withdrawn by a doctor.
  • Rubbing the rash won't spread Poison Ivy to other parts of your body (or to another person). You spread the rash only if urushiol oil has been left on your hands.
  • Although Poison Ivy and Poison Oak have 3 leaves per cluster, so do many other plants. Learning to identify Poison Ivy is important.  
  • It can cause a rash during any season and every part of the plant, including the roots, can cause a rash.
Identification of the plant can seem confusing, but with a little bit of attention, anyone can become a good identifier of poison ivy. Besides, this is one lesson in life that you do want to pay attention to and play on the safe side. Poison Ivy varies in size, shape and color. It can be found growing in any of the following three forms:
  • as a trailing vine that is 4-10 inches tall,
  • as a shrub up to 4 feet tall, and
  • as a climbing vine that grows on trees or some other support.
The woody vine can trail, straggle, or scramble over rocks. It can climb high due to aerial rootlets on its stems. These climbing vines have fibrous, hair like rootlets that attach to tree bark or other objects and look like fuzzy ropes.
My own personal "fast and dirty" method of identifying Poison Ivy is a simple two-step approach (or non-approach as it were).
  1. Check for the three leaves, making sure that the middle leaf has a longer stem than the other two, and
  2. Check if the stems are hairy.
If those two things are present, its a safe bet that you've discovered Poison Ivy. If the stem does not appear hairy, look a little more closely at the plant, if you see ANY aerial rootlets appearing anywhere on any of it's stems, its probably Toxicodendron. I also routinely assume that any vine climbing up a tree is Poison Ivy until I can prove otherwise. 

Poison Ivy climbing on tree and among shrubs
copyright SHD 2011
Methods and treatments for urushiol exposure do vary, but one product that most agree should never be used to treat poison ivy or the resulting rash, is bleach.  Just don't use it. (What's our motto, kiddies?  That's right, Don't Be Stupid.)  You will only make matters worse for yourself.

What you should do, if you know you have come into contact with Poison Ivy, is to rinse the affected area with lots of cold water, like with a garden hose. You have about 20 minues to an hour before the oil bonds with your skin. Do NOT try to rince the urushiol oil off with hot water, you will only cause your pores to open up and the oil will enter your skin faster. (However, if you already have a rash, using hot water can relieve the itching for a while.)

There are lots of over the counter remedies, including special soaps and wipes to wash off the urushiol oil immediately after exposure.  Corticosteroid skin creams or ointments may help reduce inflammation after rash occurs. Always follow the instructions carefully when using these products.  There are lots of other OTCs to relieve the rash, they all seem to work differenty for each individual.  If the rash is extremely bad, or persists longer than a week, you may need to see a doctor. 

Another method to prevent the rash immediately after exposure is to rub juice from the broken stem of jewelweed on the affected area. Plantain species also helps.

Hairy rope? Don't be a dope!
copyright SHD 2011
Poison ivy grows throughout most of North America, including eastern Canadian, all U.S. states east of the Rockies, and in the mountainous areas of Mexico. The first European to describe this plant was Captain John Smith in 1609.  It was he who coined the name "Poison Ivy." Ever since then, there has been confusion regarding this plant and its cousins.  There are no native European Toxicodendron species but, Toxicodendron radicans (Eastern Poison Ivy) was introduced to Europe as an ornamental in the 1600s.

Two different vines...which one is Poison Ivy?
The one on the right.    Copyright SHD 2011
The word Urushiol is derived from 'urushi', a Japanese name for lacquer. The Japanese take the toxic sap from the trunk of the Chinese Lacquer Tree (Toxicodendron vernicifluum, formerly Rhus verniciflua).  The sap is then filtered, heat-treated, or coloured before applying onto a base material that is to be lacquered. Curing requires "drying" it in a warm, humid closet and takes 12 to 24 hours where the urushiol polymerizes to form a clear, hard, waterproof surface. Once hardened, reactions are possible but less common.

Usually my last comments are about how to grow a plant, but for this article I'll discuss how it grows and how to eliminate it.   (Unless of course, you are a person who truely wants to grow a poison garden, or are just really sadistic.  Either way, you are on your own with this one.)

Propagation is primarily by rhizome. Leafy shoots are produced at basal stem nodes along the multi-branched rhizomes; on some sites, rhizomes may extend up to 7' beyond the parent plant. As a result of this extensive network of rhizomes, Poison Ivy frequently forms thickets under favorable site conditions. These thickets may represent a single clone or several individuals.

Commercial weed and brush killers have a mixed reputation.  Some people swear by them, others contend that only the leaves are destroyed while the roots remain to regrown later.  Most claim that the only way to get rid of Poison Ivy is to do it the old fashion way, ripping it out by hand.  Of course, you'd need to be completely covered and wearing gloves to keep from being exposed to the oil. 

There are many sites online that give good solid facts about Poison Ivy, and sadly, there are also a lot of badly written articles that seem to have done a lot of cut and paste and no real research.  So, I am going to list a few sites that I felt were worth looking at for more detailed information on Poison Ivy and the treatment of the rash that results from contact with it.  Good luck and stay safe. 

Resources include:

The Poison Garden

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