Categories of Poisonous Plant Effects
Poisonous plants are those plants that have harmful effects. It may be from touching them, inhaling their vapors, or ingesting them. The effect may be in the form of a rash, upset stomach, heart palpitations, or worse.
Mechanical Injury
Some plants have thorns and can puncture you, sometimes breaking the tips off under your skin. Blackberries, wild roses, and other brambles have recurved spines that prevent you from moving forward. Yuccas have dagger-like points that can stab you. Climbing vines such as greenbriers can wrap around your legs and scratch you with their sharp thorns.
Hawthorn's dagger–like thorn
Cactus pads are armed and dangerous. Each spine on the pad is surrounded by tufts of hairlike spines that attack when you come near the plant. They are so tiny and difficult to see that they often have to work their own way out of your skin. If not cleaned and treated, there's always a possibility of infection.
Other plants, like stinging nettle, have spines that will sting you. Hypodermic-like needles on the stems of the plants inject a compound that produces the stinging effect. Crushing up the leaves of yellow dock and rubbing them on the affected area can relieve the sting.
Allergic Reaction
An allergic reaction is an unusually sensitive response to something ordinarily not considered harmful, as with nut or wheat allergies. Since all plants can possibly cause an allergic reaction in someone, the plant that produced the allergen is not necessarily poisonous. However, there is a greater sensitivity to some plants, such as poison ivy, poison sumac, and poison oak that cause a contact dermatitis reaction in some people and are what most people think of when you mention poisonous plants.
Internal Poisoning
Internal poisoning is the most serious poisoning as a result of effects from toxic substances. Certain alkaloids affect the central nervous system while others affect the liver.
Alkaloids
Alkaloids are toxic substances that affect the central nervous system and are found in a number of wild plants. Some affect nerve function without visible effects while others act through the nervous system, including false hellebore and death camas, both in the lily family. Other alkaloids affect the liver. Crotalaria and groundsel can cause severe liver damage.
The nightshade family is well known and includes many garden plants that have both edible and poisonous parts, for example tomatoes and peppers, whose leaves are poisonous. Some nightshades, such as the ground cherry, grow wild. The fruits of the ground cherry are edible when ripe, whereas the unripe fruits are poisonous. Nightshades also include datura, which contains alkaloids that can have dramatic hallucinogenic effects and can result in convulsions and coma, even death.
Another type of alkaloid that is widely distributed in the plant kingdom is found in ergot, a fungus that grows in grain, rye, and other grasses. It produces effects similar to LSD, which was derived from it. Alkaloids derived from ergot are used as uterine-contracting drugs.
Glycosides
Glycosides are compounds that can be broken down into simple sugars plus other substances and are found in a number of plants, most of them nontoxic. The cardiac glycosides in digitalis can strengthen the heart in small amounts but can be fatal in larger quantities. Dogbane and oleander also contain cardiac glycosides and should be handled with care.
What causes the soapy froth that I sometimes see at the edge of streams or bays?
Saponins are non-cardial steroid glycosides that have a soapy-like reaction when agitated. These are the substances that are found in yucca, bouncing bet, and other plants that have been used for soap. When taken internally they can irritate the digestive system.
Cyanogenic glycosides are the most dangerous. Cyanide poisoning is the result of the breakdown of the cyanide-producing glycoside molecule found in certain members of the rose family, including wild cherries and wild plums. Scratching the bark and sniffing it for the bitter almond scent reveals the presence of the compound that breaks down into cyanide. Wilted cherry leaves have resulted in deaths of livestock and horses that grazed on trimmed branches bordering their pastures. Seeds and pits also contain this molecule.
Goitrogenic glycosides are found in members of the mustard family and can cause goiter. Persons who have hypothyroidism should only eat members of the mustard family cooked.
Oxalates
Oxalic acid is the substance that adds a lemon-like flavor to a number of wild greens, including sheep sorrel, wood sorrel, and yellow dock. Too much, however, is not good. Calcium oxalate crystals in large quantities can damage the kidneys.
Members of the Arum family, including Jack-in-the-pulpit and arrow arum, contain calcium oxalate crystals that when bitten into produce an intense burning sensation. It can cause swelling at the back of the throat and tongue, and in extreme cases, block breathing.
Resinoids and Resins
Resinoids are chemical substances left over after plant materials have been extracted and are sometimes toxic. Mountain laurel, azaleas, and other members of the heath family contain a toxic resinoid, as do members of the milkweed family, water hemlock, and mayapple. Urushiol is the resin in poison ivy that causes contact dermatitis in some people.
Water hemlock
Photosensitization
Photosensitization looks like sunburn and occurs when sunlight reacts with certain pigments that are hypersensitive to sunlight. Buckwheat and St. Johnswort are among the plants that have photosensitizing pigments and can cause one to become sensitive to the sunlight. Taking St. Johnswort or eating products that include buckwheat may cause one to burn more easily when exposed to the sun than they normally would.
Poison ivy–leaves of three
