“Leaves of three, let it be” is an old saying that warns of the dangers of poison ivy and poison oak, but those aren’t the only toxic plants out there. Learn the basics of identification, natural history, and specific lethal compounds of approximately 20 species you may encounter while hiking or foraging. In our Wild and Wicked Poisonous Plants class on July 11 with instructor Mark Manning. Leave with a solid understanding of which plants to avoid touching and consuming and which ones to keep away from pets and children!
Mt. Cuba Center: Poisonous plants are certainly an interesting area of study, what led you to want to know more about poisonous plants?
Mark Manning: Over the years, I have studied different aspects of the natural world (carnivorous plants, reptiles/amphibians, birds, basic botany) but my fascination with poisonous plants didn’t really take off until I started teaching a high-school level toxicology course. I had a basic background in general toxicology from college coursework and some exposure to it while working as a chemist, so I proposed an entry-level toxicology course to the school board and it was approved.
My vision for the course was to have a unit where we not only studied local poisonous plants in the classroom, but also went into the field to observe them directly. I went down the rabbit hole a bit researching these plants, and then ended up tracking down and finding a number of poisonous plants at two different sites in our area. These sites were then used as the end-of-course field trip site.
The poisonous plants unit ended up being very popular with the students. As shown by end-of-course surveys, their favorite part of the course was almost always the poisonous plants unit. They were almost unanimously emphatic about their enjoyment of the field trip where we discussed the natural history of the plants, as well as their toxicity and their roles in history. Two students even stated that they wanted to go on to become toxicologists after the course. My personal interest in these plants has grown from there and continues to evolve.
Mt. Cuba Center: What is the most interesting poisonous plant you’ve come across?
Mark Manning: This is a difficult question to answer, as many of these plants have interesting characteristics. Whether it is how they poison someone, how much they resemble an edible plant, their uses in history (such as their use as an arrow poison), or their overall potency, each species of poisonous plant draws my attention in some way.
I think that the one plant that still stops me in my tracks every time is water hemlock (Cicuta maculata). It is a beautiful, elegant plant, but it is deadly, and its mechanism of action is quite gruesome. Another plant that always makes me stop and look is jimsonweed (Datura stramonium). This plant is also attractive (especially its flowers) but the mechanism of toxicity is devastating.
I will save more details for the Wild and Wicked Plants program, but we will be discussing these particular plants and many others!
Mt. Cuba Center: What are some common poisonous plants found in Delaware and the surrounding areas?
Mark Manning: Regarding ingestion poisons: some of the more common native poisonous plants include (but are not limited to) jack-in-the-pulpit, water hemlock, swamp milkweed, Indian hemp/dogbane, rhododendron, mountain laurel, pokeweed, and white snakeroot.
A few non-native/invasive poisonous plants include poison hemlock and jimsonweed, which are only found occasionally, but may be common in certain areas (especially disturbed sites).
Some plants containing contact poisons include poison ivy, poison sumac, wild parsnip and cow parsnip.
All of these are found in Delaware and the surrounding area. The Mount Cuba Center has specimens of a variety of poisonous plants from many different plant families and is an outstanding resource for anyone interested in viewing or photographing these plants.
Mt. Cuba Center: Where should someone start if they want to know more about poisonous plants?
Mark Manning: By signing up for Wild and Wicked Plants, of course!
Some other resources to note include the books Wicked Plants by Amy Stewart, and Plants that Kill by Elizabeth Dauncey. Both are very good. The latter book is more technical and not a light read, but it is very comprehensive.
A good avenue for hands-on identification is to connect with a botanist/naturalist or an experienced, knowledgeable foraging instructor and have them show you the most poisonous plants in your area. This is a great springboard for learning more, and foragers often look for very specific identifying features of the plant that more casual observers will overlook.
Mt. Cuba Center: Is there anything else people considering signing up for your class should know?
Mark Manning: Yes! I’m grateful to be spending this time sharing this fascinating information with others. Toxicology is a science that evolved from the knowledge of ancient poisoners, and the sources of those poisons are the same plants that decorate our landscapes and exist in our public parks. Bring your sense of curiosity and wonder, and prepare yourself to be awed by the toxicity of these plants, what they can do to the body, and the effects that these plants have had on humans throughout our history. Some of these plants have changed the course of history! I look forward to seeing you all there.