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Poison Ivy
Toxicodendron radicans
by Tek Von Essen
Every year, nearly two million people living in the United States experience irritating
or painful effects from direct or indirect contact with poison ivy. In some degree, one
out of every two persons in the American population is allergic to this poisonous plant.
Many of us have already experienced the aggravating effects of this toxic plant.
Poison ivy is a member of the Order Sapindales, and is also a member of the cashew or
sumac Family Anacardiaceae. The plant is also commonly referred to as Rhus radicans.
It is a native throughout Asia, Canada and most of the United States. It is a remarkably
variable plant that has also been introduced in Great Britain, Europe, and Australia. With
the exception of most of the West Coast, Toxicodendron radicans vines may be
discovered in a tremendous medley of locations throughout North America. It prefers rich
soil with good drainage and an abundance of water. Poison ivy vines can be found sprawling
along the ground, in low plants, climbing high in trees, or on poles. It is commonly found
in disturbed places, along lake shores, throughout pastures and thickets, along the edges
of woods, on stream banks and fences, along roadsides and trails, in areas of waste
ground, and around buildings. It seems to prosper in slightly shaded areas. |
There is considerable debate over whether poison ivy is one species with variations, or
many independent species. Poison ivy can take shape as a perennial woody vine reaching up
to twenty meters in length, or as a shrub-like plant ranging up to two meters tall. Dense,
dark, fibrous aerial roots grow along the climbing stem. This gives the vines a hairy
look. Young leaves are green, often with a reddish tint that they lose as they mature. The
alternate compound leaves have three ovate leaflets. The leaflets are approximately twelve
to seventeen centimeters long and seven to ten centimeters wide. Each leaflet is hairless
or slightly hairy. The margin of each leaflet is coarsely toothed or lobed, with the end
of the leaflets forming a pointed tip.
Yellow-green flowers, between six and eight millimeters across, may exist on new
growth. These flowers display re-curved petals, and bloom during the months of May through
June. The small, four to five millimeter fruits, are often gray or cream-white. A papery
outer covering surrounds the shallow, longitudinal grooves and inner fibrous coat. The
fruit ripens in late summer through late fall. At approximately the same time, the leaves
turn bright red, attracting the many birds that feed on the fruits.
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The pestilent ingredient of poison ivy is called 3-n-pentadecylcatechol. This potent
chemical is found in all parts of the plant. The skin irritant resides in the sap found in
the roots, stems, leaves, pollen, flowers, and even fruits. A very itchy and sometimes
painful skin rash may result from even the slightest contact with this sap. The sap is
released when a portion of the plant becomes damaged or broken. According to various
sources, the danger of poisoning is greatest during the seasons of spring and summer. This
is the time when the sap is abundantly produced and the plant easily bruised.
In addition to direct contact with the plants, the toxin may be spread by animals,
contaminated clothing, common work tools, sports equipment, or by accidental eating of the
fruits. The irritant chemical is not volatile; however, droplets may be carried on dust
particles in smoke or ash. It is therefore dangerous to stay in the smoke generated from
burning plants. Pollen may be blown and spread by wind. This makes it is possible for an
extremely susceptible person to contact the poison simply by being in the same general
vicinity of the plant when pollen is present in the air.
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Suitable identification and knowledge of the plants are essential in prevention of
contamination. Extermination by means of digging or through chemical herbicides proves to
be the most effective means of eliminating recurring contact with the plants. While
extermination would be desirable around the house, poison ivy is valuable to wildlife and
important to the balance of nature. We must do our best to protect and preserve these wild
native plants.
Written fall 2000, as a service learning
project for Dr. Gary Coté's Biology 102 class at Radford University. Copyright Pathways
for Radford. |
