Weeds That Can Kill
DAVIS, California, September 3, 2010 (ENS) - A woman in Tacoma,
Washington who apparently died of poison on April 1 may have been killed
by hemlock after gathering the leafy green weed and using it on a salad.
Her death was no isolated incident, say weed experts. Each year
dozens of Americans die or are sickened by weeds they did not know were
harmful.
"It's an easy mistake to make," says Joseph DiTomaso, cooperative
extension specialist in the Department of Plant Sciences at the
University of California at Davis, a member of the Weed Science Society
of America and author of "Weeds of California and Other Western States."
"Hemlock and other poisonous weeds are often cousins of edible foods
and share similar flowers, leaves, fruit and seeds," said DiTomaso.
"Backyard gardeners and wild food enthusiasts need to be well-informed
in order to stay safe."
"Most plants produce their own naturally occurring pesticide to deter
predators so they won't be eaten," DiTomaso explained. "It's a very
competitive world, and no plant could survive without producing some
defense mechanism."
There are many toxic weed species, and the
Weed Science Society of
America has assembled a list of 10 that are especially dangerous.
Click
here to see images of all these poisonous weeds.
The list is topped by two very dangerous genera of hemlock.
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Poison hemlock, Conium maculatum
(Photo courtesy
WSSA)
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- Poison hemlock (Conium maculatum) is a biennial weed with
fern-like leaves that can be easily mistaken for parsley. Like
parsley, it is in the carrot family. The plant produces a number of
toxic substances, but the most deadly is the alkaloid coniine - a
neurotoxin that disrupts the central nervous system. Ingesting even
the smallest amount can result in rapid respiratory collapse and
death. One way to identify poison hemlock is by the purple-red
blotches on its stems. This is the species responsible for the death
of the Greek philosopher Socrates.
- Waterhemlocks (Cicuta douglasii and Cicuta maculata)
are also native perennials in the carrot family. They grow in
wetlands and marshes and are easily mistaken for a variety of edible
plants, including young carrots, wild celery, watercress, wild
ginseng and particularly parsnips. Like poison hemlock, water
hemlock is highly toxic. It produces a substance called cicutoxin
that stimulates the central nervous system and can trigger violent
seizures.
- Oleander (Nerium oleander) is a woody shrub often planted
in suburban landscapes and along roadsides. It is extremely toxic
and produces a poisonous substance that can cause heart arrhythmia
and cardiac arrest. DiTomaso cautions that you should never burn
oleander branches - the fumes can be hazardous. He has even heard
reports of severe illness when an oleander stick was used to roast a
hotdog over an open fire.
- Bittersweet nightshade (Solanum dulcamara) is an invasive
weed related to both tomato and potato plants. It can be extremely
toxic, and in fact, the juice from wilted leaves is deadly. The most
common type of nightshade poisoning comes from eating its green
berries, which turn red to purple in color as they mature.
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Common pokeweed or pokeberry, Phytolacca americana
(Photo courtesy
WSSA)
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- Common pokeweed or pokeberry (Phytolacca americana). All
parts of this weed are poisonous - especially the roots. "Pokeweed
greens are sometimes gathered and eaten, but they need to be
thoroughly cooked first to break down the toxins," DiTomaso says.
"If they are prepared improperly, they can be really harmful."
- Pennyroyal (Mentha pulegium) is an invasive species in
meadows or wet areas. It is known as an insect-repelling herb and is
sometimes used as a tea. It is even found in some health food stores
as an herbal medicine. But DiTomaso cautions that the weedy version
of this plant is trouble if too strong a tea is made from the
leaves. It can cause liver damage, lung damage and death. Both weed
scientists and physicians say pennyroyal should be avoided. It's not
worth the risk.
- Meadow deathcamas (Zygadenus venenosus) and other
deathcamas species are native perennials in the lily family. They
tend to grow in forested or meadowy regions. All parts of the plant
are toxic. That includes its bulb, which is easily confused with
edible wild onions. One differentiator between the two is that
deathcamas lacks the distinctive odor typical of an onion.
- Foxglove (Digitalis purpurea) is an escaped ornamental
plant that produces tall stems ringed with colorful bell-shaped
flowers. The soft leaves at its base are easily mistaken for comfrey
or sage, but lack the distinctive smell of the safer species. But
looks can be deceiving. This invasive weed is very poisonous.
DiTomaso says it produces a chemical that can speed up and
strengthen heart contractions. The leaves on the upper stem are
particularly potent; just a nibble is enough to be deadly.
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Jimsonweed, Datura stramonium
(Photo courtesy
WSSA)
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- Groundcherry (Physalis spp.) is in the tomato and potato
family. Its leaves and unripe fruit are poisonous if ingested and
can even be fatal. But the ripened fruit loses its toxicity and is
sometimes made into jellies, jams and sauces. The ripened fruit of
one species, tomatillo, is a very common ingredient of Mexican
salsas. DiTomaso says it is not unusual for the toxins in a weed's
fruit to break down with ripening. In fact, it's another survival
mechanism. If a bird, deer or other predator eats the fleshy fruit,
the seeds inside are spread and the plants multiply.
- Jimsonweed (Datura stramonium) is also in the tomato and potato
family. It produces a dangerous poison that can be fatal to humans
and animals, including livestock and pets. Jimsonweed produces seeds
that are highly hallucinogenic and can trigger bizarre and violent
behavior.
"Lots of weeds are edible, but there are many dangerous exceptions,"
DiTomaso warned.
"If you have any doubt, avoid any contact with the plant until you
can consult an extension agent or a trusted resource so you don't make a
dangerous or even deadly mistake."
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Environment News Service (ENS) 2010. All rights reserved.
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