In my last column, I talked about Italian arum being one of the poisonous plants we might find in our gardens. This week, I want to address some of the other plants in our gardens that are considered toxic or poisonous. The information contained here is from a presentation by former OSU Horticulture Extension Agent Joy Jones as given to the Master Gardener class each year.
First, allow me to address the meaning of the word “poison.” For the purposes of this discussion, “poisonous” does not necessarily mean lethal. Some plants will cause dermatitis while others can cause illness if ingested but are perfectly safe to have in the garden as long as they are not eaten. The term “poisonous plant” refers to plants that have some sort of properties that can be harmful to human or animals.
These plants may cause skin irritation or allergies. Think poison ivy, poison sumac or poison oak. Others may cause burning or irritation in the mouth or throat if swallowed. Headaches, dizziness or nervous excitement may also be symptoms as are upset stomachs, nausea or vomiting. And the dose that is consumed will determine the toxicity of the plant poison. Another group of factors that determines toxicity is the age, weight and overall health of the victim, the stage of growth of the plant itself, and the parts and condition of the plant consumed.
Plants are pretty tricky and have their own sets of defenses since they can’t move out of the way of danger. A browsing elk, for example, could wipe out a whole section of plants in a matter of hours so the plants produce a bitter taste or a chemical that will cause herbivores to become sick, making it less likely they will try to eat that same plant again. Tomatoes or apples eaten when green have an intestinal irritant that will make us think twice before sampling them again. As the fruit ripens, however, the toxicity decreases and the flavor increases that attracts animals into eating them, thus dispersing the ripened seeds.
The leaves and berries of English ivy are both toxic and cause gastrointestinal issues like nausea and swelling of the tongue and lips. Bulbs of daffodils and jonquils and the iris corms and leaves have the same issues. When harvesting rhubarb, eat only the petioles and not the raw or cooked leaves.
Plants containing Taxine Alkaloids are considered to be very toxic and these include English and Pacific yews, wild and ornamental lupines, delphiniums and poppies. In one to three hours, ingestion of these plants or their parts can cause dilated pupils, dizziness, increased heart rate and convulsions. Victims may fall into a coma and death can occur in less than 30 minutes in some severe cases.
Rhododendron and azalea – even the ones native to the United States – contain Grayanotoxins. These toxins can cause dizziness, vomiting and weakness, but it is rarely fatal and usually subsides in 12 to 24 hours. Grayanotoxins can become an issue, though, if consuming honey made from rhododendron nectar. (In fact, knowledge of “Mad Honey Intoxication” goes back to 4th century Greece when thousands of soldiers were poisoned by rhododendron honey.) Not all rhododendron produce Grayanotoxins, but the Pacific rhodie, the Western azalea and Rhododendron albiflorum all do produce it. Mountain Laurel and Japanese Pieris do as well.
There are other plants and other toxins and I encourage you to do some
out what plants are dangerous. In the meantime, there are things you can do to prevent plant poisonings in your garden.
Number one is to identify all the plants in your yard – and don’t forget the house plants! You will need to know their botanical names as well as their common names. Label your plants or make diagrams of where they are located in your garden/home. After you know all the plants, make notes as to which ones are poisonous and what the effects of their particular toxins are. That should go on the label or maps, too.
Teach children not to put any type of plant in their mouths unless it is cleared by you or a knowledgeable adult. Don’t let children suck the nectar from flowers or make tea from its leaves. Know the plants when you are harvesting berries or fruit. Just because birds or wildlife eat a berry doesn’t mean it is safe for human consumption! If mushrooms or toadstools are growing in your yard, dig them out and dispose of them, especially if you don’t know what species they are. When you are roasting marshmallows or meat over a fire, make sure you know what kind of wood has been cut for the skewers. Oleander branches or sticks, for example, are extremely toxic.
If a person has ingested a toxic plant and is having trouble breathing, unconscious or having seizures, call 911. It is helpful to know what they have eaten and to take a sample in a plastic bag with you when you go to the hospital. In less-life threatening emergencies, call the Oregon Poison Center at OHSU (1-800-222-1222) – a good number to memorize. If a pet is the victim, call the Pet Poison Helpline at 1-855- 764-7661. You may not know what your pet ate, but if you do, be sure to tell the operator. For photographs of many poisonous plants, you can visit https://plants.usda. gov/gallery.html.
We can’t really remove all of the poisonous plants from our environment, but we can remove the most dangerous ones. Or at least place them in an area where children and pets do not frequent.