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(HealthNewsDigest.com) – There are several plants that can cause irritation when touched. These are also considered toxic plants and should not be ingested. The most common of these is the well-known poison ivy, but it is a bit of a challenge for most
people to tell the differences between poison ivy and poison oak. If you spend time in the woods or gardening in the yard, it would be beneficial to know which plants are the ³don¹t touch me plants.² This article looks at several of the plants in Indiana that can produce problems when touched.
Some of you may already have experienced the itch of poison ivy or the
burning and welting of stinging nettle.
Poison Ivy and Poison Oak
The telltale sign that you could be looking at poison Ivy
(Toxicodendronradicans – eastern poison ivy or T. rydbergii – western poison
ivy, Indiana has both) or Atlantic poison oak (T. pubesens) is the
characteristic trifoliate leaf. The two opposite leaflets will have very
little or no petiole and the terminal leaflet will be extended from the two
opposite leaflets (Figure 1 and 2). There are other plants that might have a
similar leaf, but it might be wise to treat everything with this leaf
arrangement as potential poison ivy. According to the USDA plant database,
poison oak has not been reported in Indiana as of yet, but it has been
reported in Illinois. However, although the USDA has not officially
confirmed poison oak in Indiana, I have received word-of-mouth reports that
it is present.
Poison ivy can grow as a vine or low shrub. It will climb trees, power line
poles, fences or just about anything available to climb. Poison oak is a
shrub with hairy leaves that have an oak-leaf appearance, hence the name.
Both plants produce greenish-white berries which birds eat, spreading the
seed. In the winter time, the berries still have the oils that cause
dermatitis so they need to be avoided also. Decreases in cases of poison ivy
in the winter time is most likely due to the extra clothing worn to fight
the cold.
The compound that causes all the trouble is urushiol oil or toxicodendrol.
Although sensitivity to urushiol oil can be different for different
individuals, very small amounts are generally required to cause a rash.
Sensitivity to the oils can also change as a person gets older. Although I
have spent a fair amount of time in the woods and have come in contact with
poison ivy, I have yet to experience the displeasure of the rash, yet this
may change one day. Other people that I know are often fond of saying, ³If I
even see the stuff I break out in a rash.²
The oils can last for a long time on surfaces. The use of water alone will
not remove the oils and in some cases water alone can spread the oils. To
remove the oils wash skin or clothes with an alkaloid soap. Alcohol will
also remove oils. There have been many proposed treatments of poison ivy
dermatitis. In the ³Peterson Field Guide to Edible Wild Plants² it mentions
that washing with Jewelweed (Impatiens capensis) juice can be used as a
home.
A 1902 report in The American Journal of Nursing, it mentions, ³Šbathing the
affected parts with a solution of sugar of lead (lead acetate), with the
addition of laudanum.² I can see where the laudanum (an opiate) would reduce
the discomfort, but I would not attempt this at home. The same report
mentions turning to a solution of water, alchohol, witch-hazel, and ammonia.
Poison Sumac
A shrub or small tree, poison sumac (T. vernix) can be more toxic than
poison ivy. Plants can grow from six to 20 feet tall. The compound leaves
have seven to 13 leaflets with smooth margins and the leaflets are elliptic
to oblong. Flowers are green and approximately 1/16 of an inch in diameter.
There are other sumacs in the state of Indiana that are not toxic. Although
poison sumac has been moved to the Toxicodendron genus, the other sumacs
remain in the Rhus genus. The USDA plant database reports fragrant, winged,
smooth, Northern smooth, and staghorn sumac in Indiana and the surrounding
states. These are often used for landscaping. The number of leaflets are
often the same between the toxic poison sumac and its nontoxic counter
parts. One way to help identify between the nontoxic sumacs and poison sumac
is that the berries of poison sumac are hairless, drooping, and are green
when immature, but then turn grey-white as they mature. The berries of other
non-toxic sumacs often have hairs on the berries and are red to crimson.
Another way poison sumac can be differentiated from the non-toxic sumacs is
by carefully looking at the leaves. Poison sumac leaflets are entire and do
not have a winged rachis. Non-toxic sumacs either have serrations on the
margins of the leaves, like staghorn sumac (Rhus hirta) and smooth sumac (R.
glabra) or have entire leaves but with a winged rachis, as in winged sumac
(R. copallina).
Poison Hemlock
At first glance poison hemlock (Conium maculatum) may appear like wild
carrot (Daucus carrota) or some kind of giant parsley, but it is not a
mistake that you should make. Although poison hemlock is more known for
poisonings as a result of ingesting, for example the death of the Greek
philosopher Socrates, the plant¹s natural oils may absorb through the skin.
So if you find yourself hand pulling poison hemlock, it would be a good idea
to wear gloves.
Both poison hemlock and wild carrot belong to the parsley family (Apiaceae).
Both have the characteristic umbel inflorescence of small white flowers and
leaves that expand at the bases sheathing the stems. You can tell poison
hemlock apart from its benign cousin, wild carrot, by the presence of purple
blotches on the stem. The leaves of poison hemlock are also sharper in
detail compared to wild carrot.
Continued on next page
Cow Parsnip and Giant Hogweed
Also members of the parsley family, both these plants can cause a reaction
to sunlight called phytophotodermatitis. However, the reaction from giant
hogweed (Heracleum mantegazzianum) is more severe than that of cow parsnip
(H. maximum), resulting in large blisters and red to purple rashes that can
scar. Giant hogweed is NOT common in Indiana; only two plants have been
reported to date as of writing this article. However, it has been reported
in 11 counties in Michigan. Cow parsnip, although not that common, can be
found in Indiana and is often confused with giant hogweed. Reactions to both
these two plants are dependent on an individual¹s sensitivity, but they both
require ultraviolet light to cause damage. The compounds found in these
plants that cause this reaction are suspected to be used in these plants as
protection against UV light because of their ability to absorb UV light.
The first indication that you are looking at giant hogweed is the plants
sheer stature. Giant hogweed can reach a height of 15 feet tall. Its stems
can be up to 4 inches in diameter, and its leaves can be 5 feet broad. Even
the inflorescence is large, up to 2.5 feet wide. Cow parsnip can reach up to
8 feet, but are more commonly 4 to 5 feet tall. The stem has a diameter
of at most 2 inches and leaves can get up to 2.5 feet broad. Although cow
parsnip has lobed leaves, they are not as detailed and deeply loped as giant
hogweed¹s. The stems of cow parsnip are green or light purple and have fine
hairs giving it a fuzzy appearance, but giant hogweed has coarse hairs and
purple blotches. These hairs are most noticeable where they circle the stem
at the nodes.
Stinging Nettle
Stinging nettle (Urtica dioica L.) is a very common sight in the woods, on
the banks of rivers, and in waste areas in Indiana (Figure 6). Touching
stinging nettle can produce itching and welts; walking though stinging
nettle with shorts or sandals is not advised. Stinging nettle is armed with
small hairs that, when touched, can inject a cocktail of histamine,
serotonin, acetylcholine and formic acid. Histamine causes an immune
reaction in the body, serotonin and acetylcholine are neural transmitters
and formic acid is the same compound involved in bee stings and fire ant
bites.
Stinging nettle often grows in patches and can become quite tall, growing up
to 5 feet, but I generally see it between 2 to 3 feet tall. Stems are
unbranched and leaves are opposite, egg shaped and with serrated margins.
Stinging nettle can be confused with a couple other plants in Indiana, such
as white snakeroot (Ageratina altissima or Eupatorium rugosum), Canadian
clearweed (Pilea pumila), and smallspike false nettle (Boehmeria
cylindrical). To identify stinging nettle, look carefully at the stems to
see if the obvious stinging hairs are present.
Spurges
The plants in North America that belong to the group of plants called the
spurges (Euphorbia spp. or Chamaesyce spp.) often have a milky sap that is
an acrid latex compound. This sap is a mild skin irritant, but is also
poisonous and is considered a carcinogenic. Like cow
parsnip and giant hogweed above, exposure to the sun induces irritation.
There are many plants that belong to this group. They include such notables
as poinsettia, prostrate spurge, spotted spurge, and leafy spurge. This is a
large group of plants that includes several species, but a common uniting
feature is a three chambered ovary leading to a three lobed capsule. If you
have ever inspected a Christmas poinsettia you would see these capsules
nestled in the colorful bracts of the plant.
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