I was once shown that in 'Peterson's Guide to Edible Plants of the East' it said that wild columbine was potentially toxic. Heck, as a child my brothers and I would fight over who got to eat the most columbine flowers. I made it to 46 years old without dropping over dead. lol
Some warnings just bug the crap out of me. Such as "don't gather wild edibles near roadsides." When I read this warning I often wonder if people know where their farm food comes from. Most of that food in the grocery store was planted by diesel spewing tractors, in fields covered with chemicals, that are close to the road so the farmer doesn't have to drive miles in to plant and harvest his crop. Why are there no warnings on THAT? It would still be safer to gather dandelions growing on the side of the road than eating some of the stuff on the store shelves!
Still, warnings are not a bad thing. All information should be given, so that people can make informed decisions. People just need to not read warnings and then give up on working with wild medicinals or herbs because of them.
I always say that there are light and dark medicines, meaning some medicines are easy to work with and have few bad effects on the body. Others are harder to work with and can be dangerous in wrong situations but life savers in others. It is up to the person to use their judgement on whether they should use it or not. Then, (just to confuse some) even the light medicines should be known that they can have some harmful effects, while some poisons can be used to help. The three examples I give when I do plant walks are wild rosehips, black cherry, and bloodroot.
Wild rosehips are a pretty light medicine. I add them to many tinctures or syrups that I am making. If I'm making a yarrow tea for fever I will often toss in a handful of rose hips for the added boost of vitamin C. A body often craves that dose of C when its immune system is working overtime. When teaching about wild rosehips I don't worry that someone will use it the wrong way because if they overdose on wild rosehips, their body will just shed the extra with no damage done. Now, there is one problem with this way of thinking. Our bodies shed vitamin C by pulling moisture out of our tissue, diluting the vitamin C and then sending it out in either urine, soften stool, or through sweat. If you already have diarrhea, you certainly don't want any extra vitamin C. But in our modern day world where we have plenty of safe water to drink, losing a bit of moisture from our tissue is no big deal. Just drink water to replace it. In a survival situation where your water may be limited, you might want to not overdose on any vitamin C rich foods. However right now, the little bit of problem that can be cause by overdosing on rosehips is well offset by the good it does for your immune system.
If you just read those warning about rosehips and decided that you are never going to try that "dangerous" herb, you take warnings waaayyyy too seriously. Rosehips are safer than most things we put into and onto our bodies.
The next medicine is black cherry, of which we use the inner bark. This is a 50/50 light/dark medicine. As long as you gather the inner bark after the leaves have grown to full size in the summer and before the leaves start dying back in the fall, you have a safe and wonderful cough medicine. I like to either heat the bark in water over a low heat on the stove for a few hours, then mix it with honey (this is for a fast cough medicine) or put the bark into honey and let it set in a dark place for at least six months for a longer lasting but slower cough medicine. Heck, I might even add a handful of dried rosehips to that too.
But if you gather black cherry inner bark when there are no leaves on the tree, such as this time of year, there is a poison similar to cyanide in it. It is in the leaves while they are on the tree, but when the leaves die back, that poison goes back into the tree. For an adult it wouldn't probably kill you, but both children and cattle have died from eating the wrong parts of the black cherry at the wrong time. So this wonderful and very safe medicine if you gather it in the summer, can potentially become a killer if you gather it in the winter. As I said, almost straight up 50/50 for light and dark medicine.
The last herb I talk about is bloodroot. Bloodroot is a poison. If you eat the juices raw you will regret it or you won't live to regret it. If you have delicate skin and the raw juices drop onto your skin, it can burn a hole in your skin. If you get bloodroot juice in a cut, you will know it. It's like getting acid drop into your skin. Not fun at all. This is a dark, dark medicine. People can get hurt if they gather, prepare, and use it the wrong way.
So then why use it? Because sometimes our greatest poisons are our strongest medicines. Bloodroot, simmered in olive oil with some plantain (and comfrey too if you want) for overnight, then mixed with beeswax is called black salve. This is true black salve, not the fake stuff some people call black salve. True black salve will ALWAYS have bloodroot in it.
Black salve can by dabbed onto skin cancer and it will eat only the cancer cells and it will eat ALL the cancer cells. It is something that is used with caution because often the cancer you see on the outside is only the tip of the iceberg. There are people who had a small skin tag on their nose who dabbed a bit of black salve onto it and they lost a good part of their nose because the cancer had spread under the skin. I have used black salve on an older friend who had small irregular "moles" on his arms. One, the black salve did nothing to, it was not cancerous. Two others, the black salve turned the cancer hard as a rock and after two weeks, it just fell out. Black salve can save lives.
If that is not enough, when I was a very small girl one of my father's brother cut himself with an ax. It was in winter and the wound was forgotten about under all his winter cloths until it really began to hurt. By the time he really got around to dealing with it weeks later it had begun to go gangrenous. If you have ever smelled gangrene, you will never forget that sickly sweet smell of rotting flesh. It stays with your forever. My uncle smeared black salve over the wound and the salve ate all the unhealthy tissue, leaving him with a huge scar, but he lived. So this dark medicine, that should only be used in dire need, can save a life.
Light and dark medicine is something that most healers know about, even if they use terms that they are more comfortable with. When you take your medicine into your own hands, whether it be from a doctor's care or from your garden, or from the wilds, you must always take care. But that doesn't mean you don't heal yourself because of fear. Medicine is part of life, even many animals will get to certain clays or eat plants to feel better. Ever see your dog eating grass to throw up? Medicines need to be respected, some more than others, but not feared so much we don't use them. Most of our modern day, lab created medicines are just as dangerous. It is just in our society they are advertised with flashy logos so they seem normal to take, while picking a leaf is...well...weird. A hundred years ago, it would have been the opposite.