One of our favorite summer flower natives, that’s looking great in the water garden now, is the stunning water hemlock, Cicuta maculata. Although it’s native across all of North America, it’s rarely grown in gardens. Perhaps this is because nurseries like us, are terrified to offer a perennial plant that contains such a highly effective neurotoxin.
It’s European cousin, the biennial, Conium maculatum (poison hemlock), is not nearly as toxic, but is far more famous, having taken out the Greek philosopher, Socrates. While Conium contains coniine, Cicuta does its dirty work with cicutoxin. Interestingly, black swallowtails devour both plants as a food source. Evolutionarily, they have developed biochemical defenses that allow them to consume the toxic plant with no ill effects.
I have to laugh each year, when our local television stations go into a full-blown, panty-wad panic, because someone has found a plant of the European Conium maculatum (water hemlock), and rage about how it’s an invasive species that might kill off society, as we know it, if its’ not reported and eliminated immediately. The native Cicuta maculata is 1,000 times more widespread, and far more toxic. Cicuta typically grows in very wet soils, while Conium prefers much drier, upland sites, but both are closely related members of the carrot family (Apiaceae). Both plants grow 6-8′ tall and flower in July and August, and look quite similar. You’d need to be a decent-trained taxonomist to tell the difference.
All parts of both plants are toxic, but our native Cicuta maculata stores most of its toxins in the roots and underground tubers. With Conium maculatum (poison hemlock), 6-8 leaves can take out a human, and 10-15 ounces can take out a full-sized cow in 1-3 hours. Thankfully, cows don’t like it, as long as there are other plants to eat. With Cicuta maculata (water hemlock), a 3.5 ounce piece of root is all it takes to send a human to the promised land, while a silver-dollar sized piece of root can deprive you of a potential freezer full of steaks.
Now, let’s put this in a bit of perspective. Most top 10 toxic plants in the world lists, include both of these, but also includes a few other plants that might surprise you. Two are Nerium oleander (oleander), which graces most planted highway medians and beach towns in the southeastern US, and Ricinus communis (castor bean), which is commonly cultivated as a fast-growing annual. The other plant from the top 10 most toxic plant list, that may surprise those with their heads firmly planted in the sand, is smoking tobacco, Nicotiana tabucum. Not only are there massive tobacco fields throughout the country, but I’ve always found it ironic that assisted suicide is still illegal in the US, yet people buying cigarettes for others is never prosecuted. How logical is that?
Does the hemlock have seed heads that make you think it might be dill seeds?
Thx.
Yes, they certainly do.
I made a lovely discovery, quite by accident, this summer in that you can get the effect of these lovely plants simply by leaving a few carrots in the garden over the winter and when they start to grow again, just leave them be. I have a few in full bloom right now and the effect is gorgeous.
Indeed, but they don’t reach 7′ tall.
Ricin, of course, was the toxin used by the KGB in the umbrella-stab assassination in London. There’s also the less potent Datura stramonium, which Haitian witch doctors use in a maintenance dose to keep unpopular members of the community as zombies, after having poisoned them with tetrodotoxin from a pufferfish, buried them in a comatose state and then exhumed them.
Indeed, many more on the top horticultural hit list.