closeup of water hemlock specimen

Wicked Plants of Minnesota

As told by our herbarium collections manager

Published08/29/2019 , by Tim Whitfeld

Ahead of our Wicked Plants exhibit, opening September 21, we checked in with Tim Whitfeld at the herbarium to find out which plants he considers the wickedest around. The photos are courtesy of the Minnesota Biodiversity Atlas. Here are his top three:

Poison hemlock (Conium maculatum)

An image from the Biodiversity Atlas of poison hemlock

Poison hemlock is both invasive and deadly poisonous! Native to Europe, northern Africa, and western Asia, it was introduced to North America as a garden plant in the 19th century. It’s not common in Minnesota, but there are records from areas around the state. The plant contains the alkaloid compound conniine that causes neuromuscular blockages, muscular paralysis, and renal failure. This was the species that was used to execute Socrates in ancient Greece. The plant also kills livestock. Even worse, its leaves look similar to parsley and other members of the carrot family, so it is sometimes eaten accidentally.

Water hemlock (Cicuta maculata)

An image of water Hemlock from the Biodiversity Atlas

The native species water hemlock is closely related to poison hemlock, and is even more deadly. In fact, it’s considered to be the most poisonous plant in North America. It contains cicutoxin (most concentrated in the roots but present throughout the plant) that causes violent and painful convulsions and death. It also kills livestock.

Buckthorn (Rhamnus cathartica)

Buckthorn image from the Biodiversity Atlas

Buckthorn is one of the most abundant and pernicious forest invasives across Minnesota. It’s most common in the southern and western parts of the state, but also scattered around the northeast. Besides forming dense thickets that crowd out other native shrubs and shade out wildflowers, buckthorn leafs out earlier in the spring than other native shrubs and holds its leaves longer into the fall; its longer growing season gives it an advantage and helps it out-compete native plant species.

The juicy black buckthorn berries are a favorite of birds, which only helps it take over. The scientific name of the species, “cathartica,” relates to the “cathartic” effect the plant has on the digestion system (i.e., the birds that eat the fruits experience a cleansing of sorts and they spread the seeds over the landscape).