Successful understanding of plants in a survival situation depends on positive identification. Knowing the most common poisonous plants to humans is as important a skill to your repertoire of survival skills as knowing edible plants.
Understanding Poisonous Plants to Humans Is Key in a Survival Situation
All About Poisonous Plants
It is to your benefit to learn as much about plants — both non-poisonous and poisonous — as possible. Many poisonous plants to humans look like their edible relatives or like other edible plants. For example, poison hemlock appears very similar to wild carrot.
Certain plants are safe to eat in certain seasons or stages of growth and poisonous in other stages. For example, the leaves of the pokeweed are edible when it first starts to grow, but it soon becomes poisonous.
You can eat some plants and their fruits only when they are ripe. For example, the ripe fruit of mayapple is edible, but all other parts and the green fruit are poisonous.
Some plants contain both edible and poisonous parts; potatoes and tomatoes are common plant foods, but their green parts are poisonous.
Some plants become toxic after wilting. For example, when the black cherry starts to wilt, hydrocyanic acid develops. Specific preparation methods make some plants edible that are poisonous raw. You can eat the thinly sliced and thoroughly dried corms (drying may take a year) of the jack-in-the-pulpit, but they are poisonous if not thoroughly dried.
Learn to identify and use plants before a survival situation. Some offline sources of information about poisonous plants to humans include pamphlets, books, films, nature trails, botanical gardens, local markets, and natives to the area. Gather and cross-reference information from as many of these as possible, because many sources will not contain all the information needed about poisonous plants to humans.
Rules for Avoiding Poisonous Plants
Your best policy for survival is to be able to look at a plant and identify it with certainty and to know its uses or dangers. Many times this is not possible, however.
If you have little or no knowledge of the local vegetation, use the rules to select plants for the “Universal Edibility Test.” Remember, avoid:
- All mushrooms. Mushroom identification is very difficult and must be precise, even more so than with other plants. Some mushrooms cause death very quickly. Some mushrooms have no known antidote. Two general types of mushroom poisoning are gastrointestinal and central nervous system. Neither are pleasant.
- Contact with or touching plants unnecessarily.
How Plants Poison Humans
Generally, plants poison humans by one of three means:
- Ingestion. When a person eats a part of a poisonous plant.
- Contact. When a person makes contact with a poisonous plant that causes any type of skin irritation or dermatitis.
- Absorption or inhalation. When a person either absorbs the poison through the skin or inhales it into the respiratory system.
Plant poisoning in humans ranges from minor irritation to death. A common question is, “How poisonous is this plant?”
As with all worthwhile questions in life, the short answer is: it depends. It is difficult to say how poisonous plants are because:
- Some plants require contact with a large amount of the plant by a human being before noticing any adverse reaction, while others cause death with only a minuscule amount.
- Every plant will vary in the amount of toxins it contains due subtle variations in subspecies, as well as different growing conditions.
- Every human has a different level of resistance to toxic substances.
- Some may be more sensitive to a particular plant.
Some common misconceptions about poisonous plants are:
- Watch the animals and eat what they eat. This statement is usually true, but some animals can eat plants that are poisonous to humans.
- Boil the plant in water and any poisons will be removed. Boiling removes many poisons, but not all.
- Plants with a red color are poisonous. Some plants that are red are poisonous, but not all.
The key point here is that there is no one rule to aid in identifying poisonous plants to humans. Which is why you must make an effort to learn as much about them as possible.
Contact dermatitis from plants will usually cause the most trouble in the field. The effects may be persistent, spread by scratching, and are particularly dangerous if there is contact in or around the eyes.
The principal toxin of these plants is usually an oil that gets on the skin upon contact with the plant. The oil can also get on equipment and then infect whoever touches the equipment. Never burn a contact poisonous plant because the smoke may be as harmful as the plant. There is a greater danger of being affected when overheated and sweating. The infection may be local or it may spread over the body.
Symptoms may take from a few hours to several days to appear. Signs and symptoms can include burning, reddening, itching, swelling, and blisters.
When you first contact the poisonous plants or the first symptoms appear, try to remove the oil by washing with soap and cold water. If water is not available, wipe your skin repeatedly with dirt or sand.
Do not use dirt if blisters have developed. The dirt may break open the blisters and leave the body open to infection. After you have removed the oil, dry the area. You can wash with a tannic acid solution and crush and rub jewelweed on the affected area to treat plant-caused rashes. You can make tannic acid from oak bark.
Common poisonous plants that cause contact dermatitis in humans are:
- Poison ivy
- Poison oak
- Poison sumac
- Rengas tree
- Trumpet vine
Ingestion poisoning for humans can be very serious and could lead to death very quickly. Do not eat any plant unless you have positively identified it first. Keep a log of all plants eaten.
Signs and symptoms of ingestion poisoning can include nausea, vomiting, diarrhea, abdominal cramps, depressed heartbeat and respiration, headaches, hallucinations, dry mouth, unconsciousness, coma, and (obviously) death.
If you suspect plant poisoning, try to remove the poisonous material from the victim’s mouth and stomach as soon as possible. Induce vomiting by tickling the back of his throat or by giving him warm saltwater, if he is conscious. Dilute the poison by administering large quantities of water or milk, if he is conscious.
The following plants can cause ingestion poisoning if eaten:
- Castor bean
- Death camas
- Physic nut
- Poison and water hemlocks
- Rosary pea
- Strychnine tree
For a complete guide to poisonous plants for humans, we highly recommend A Field Guide to Venomous Animals and Poisonous Plants: North America North of Mexico.