Herself’s Houston Garden

So what is it that makes one plant poison and another food? It is the chemical compounds in the plant. Some poisonous plants have several of these toxins, some only one.

Alkaloids
This is a large group of nitrogen compounds and the most common of plant toxins. Over 20% of plants contain an alkaloids. Mixed with salts they form medicines or poisons. They usually have a bitter taste. One of the first clues a plant might be toxic is taste. Any unknown plant with a bitter taste should be suspect.
Alkaloids are often the hallucinogenic compound in a plant.
(jimson weed, angel’s trumpet, henbane, deadly nightshade, mandrake)
Plant poisoning alkaloids

Glycosides
These are converted to sugar and non-sugar compounds by hydrolysis. The non-sugar part contains the toxin. Often used as heart or stomach medicine, in the wrong dose they kill. They block ATP production, which prevents you from making energy, causing rapid death.
( digitalis, olenander, lily of the valley, squill, bamboo, elderberry )
Plant Poisoning Glycosides

Oxalates
Oxalates are carbon based acids that are corrosive. They form tiny crystals that cause damage when ingested. The pain is usually strong enough that people do not continue to eat the plant. Often plants containing oxalates have heart shaped leaves that tend to be large.
( philodendron, dumb cane, rhubarb, taros, agaves )
Oxalates: Adverse drug of the month

Proteins
These only occur rarely in plants, but are the most powerful of all the toxins. They are currently being researched for their anti-fungal abilities.
( rosary beans, castor beans, some latex )
Peas and beans gone bad

Amines
Nitrogen compounds. These cause degeneration of motor tract, leading to paralysis and death.
( sweet peas, mistletoe, poison vetches )

Polypeptides
Cause cellular degeneration of internal organs such as livers.
( deathcap mushrooms )

Resins and resinoids
Sap that hardens into a hard glossy material.
(poison ivy, milkweed, rhodendron, mountain laurel, some pines )

Mineral toxins
Some plants uptake toxins from the soil
( poison vetches )

Alcohol
Alcohol is common in plants, but rarely toxic. When it is toxic it is extremely toxic. There are two main alcohol toxins: cicutoxins and oenanthotoxins found in water hemlocks that cause seizures. The second contains tremetones found in plants like snake root.
( water hemlock, white snake root )

Urushiol
This causes skin irritations and itching. It is the liquid of the plant that causes the problem.
( poison ivy, poison oak )

See also:
Texas Toxic Plants

Plants whose roots had been inoculated with Bacillus subtillis remained healthy when exposed to Pseudomanas syringae bacteria. B subtillis is often added to soil to protect plants in commercial environments.

When attacked by the bacteria a signal travels from the leaves to the roots of the plant and the roots excrete malic acid. The carbon rich malic acid attracts b subtillis.

11:39 a.m., Oct. 17, 2008—-Researchers at the University of Delaware have discovered that when the leaf of a plant is under attack by a pathogen, it can send out an S.O.S. to the roots for help, and the roots will respond by secreting an acid that brings beneficial bacteria to the rescue.

The finding quashes the misperception that plants are “sitting ducks”–at the mercy of passing pathogens–and sheds new light on a sophisticated signaling system inside plants that rivals the nervous system in humans and animals.

The research was led by Harsh Bais, assistant professor of plant and soil sciences at UD, former postdoctoral researcher Thimmaraju Rudrappa, who is now a research scientist at the DuPont Co., Kirk Czymmek, associate professor of biological sciences and director of UD’s Bio-Imaging Center, and Paul Paré, a biochemist at Texas Tech University.

The study is reported in the November issue of Plant Physiology and also is featured on the journal’s cover. Rudrappa is the lead author of the research paper. . . .

read more

One of the first things I noticed as a gardener down here was that every plant had thorns, or was toxic or both. It’s a harsh environment.

A few months back I had the pleasure of attending ‘Murderous Plants and Poisonous Herbs’ talk given by Barney Lipscomb. If you have a chance to see it, don’t miss the talk.

It started me thinking more about what makes a plant toxic and which plants are toxic. So I’ll be digging into all sorts of cool information about toxicity, plants, and poison for a bit. I’ve a huge stack of books on toxic plants piled on my desk and a longer list of websites to dig through. Homeland Security should be showing up any day now. I’ll try to get these written before they come take me away.

Unintentional death by poison happens to about 8 people per 100,000 per year. In 2005 23,618 people were died from accidental poison. While that does not sound like much, poisoning death rates have doubled from 1985-2004. Death by poison is second only motor vehicle deaths in accidental death totals nationwide.

Accidental death by poison mostly occurs in people 15 to 65 years of age. If you are between 34-53 you are more likely to die by poison then in a motor vehicle wreck.

As with any substance, ‘The dose makes the poison’. Water can kill you if there is enough of it to prevent you from breathing, or if you drink enough to upset your body chemistry.

Toxic doses are measured in LD 50, which refers to the dose will kill 50% of the healthy adults who are exposed to it. ( LD Lethal Dose )

Somewhere around 700 known toxic plants grow in the United States.

Should you ever need immediate help or have a question about a poison, call 1-800-222-1222. If you have come into contact with a substance you are not sure about, keep some handy for identification or at the very least take a photo. Treatment depends on proper identification.

How do accidental poisons happen? Most of them occur in hospitals when the wrong medicine or dose is given to a patient. In the world outside it is from misidentified plants. Know your plants. Google image search is great for finding plant names. But use a trust but verify method. I’ve seen many misnamed on the web. Find your plant, then verify, it is the correct name for the plant using another source.

More information:
NCHS Accidents/Unintentional Injuries
SciAm: Strange but true: Drinking too much water can kill

If you are wondering about the soil around your home the best thing you can do is a Soil test. Send it to your local extension office or use a do it yourself kit.

Another great source of soil information is the USDA Web Soil Survey You can zoom in on the map to your location and get all sorts of information about your soil.

Wander about the site, you’ll find enough data to spend an afternoon wandering.

Like most government sites the use is not intuitive or clearly explained.

Click the ‘Web Soil Survey’ link ( top right section of website )Web Soil Survey

Select ‘Navigate by Address’ and put in your address and click ‘View’

Now you must select an area of interest using the ‘aoi’ buttons on the top of the map. Click one of them and use it to select the area of the map you are interested in.

Once you have an area selected you can choose the ‘Soil Map’ and ‘Soil Data Explorer’ tabs to obtain information.