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Poison ivy can drive you crazy, hemlock's worse

• Herb Broda: Nature Notebook
• June 27, 2020
• 2736

Imagine shopping for garden plants and including poison ivy on the list. Sounds ridiculous, but there was a time when poison-ivy seeds were nearly worth their weight in gold.

It goes back to the early 1600s when Capt. John Smith of Jamestown began to encourage Virginia farmers to grow poison ivy for export to Europe. To understand the poison-ivy craze, you have to visualize the gardens of Europe in the 1600s.

European gardens were very green, but they lacked the variety of colors we see in gardens today. Plant historian Anita Sanchez notes that as flashy species of plants like petunias and daylilies began to be imported, the demand for colorful plants grew.

So why poison ivy? Although the plant is green during the summer, it’s one of the first to change color in the fall and can glow a brilliant red, yellow or orange. It was exactly the splash of color wealthy landowners wanted for their gardens.

Even monarchs loved poison ivy. The formal gardens at Versailles included the plant for several decades, and Marie Antoinette and Josephine Bonaparte grew poison ivy in their private estates. Even Thomas Jefferson grew it in his garden at Monticello as an ornamental plant.

Over time, however, the nasty rash and difficulty of containing the plant in one place undercut it as a status symbol. Birds would eat the berries and then disperse the seeds everywhere, making poison ivy no longer a rare plant signaling wealth.

Today poison ivy is everywhere. It’s often seen as a tree vine but also grows on the ground as individual plants or as a shrub. Leaves are in clusters of three and now are turning a beautiful shade of green. As a vine, it has thick, hairy roots that attach to the tree.

The ivy itch comes from a substance called urushiol. It’s found in all parts of the plant — the roots, stems and leaves. Even if the plant is dead, it still can cause skin irritation for years, and residue on unwashed tools or clothing can hold the oil for several months.

Life-threatening urushiol exposure can occur when brush or logs are burned that include poison-ivy leaves or roots. The oil can be carried in the smoke, potentially causing severe internal systemic complications requiring immediate medical attention. Don’t burn it.

Poison ivy has always supported wildlife and is one of our most important native plant food sources. The small white berries ripen in late summer and last into winter, providing a stable food source for dozens of bird species. Deer, raccoons and rabbits also eat the roots, stems and leaves while many insects also find food and shelter in the plant.

The future of poison ivy could be good for wildlife, not so good for us. Some researchers have found the increasing levels of carbon dioxide associated with climate change can result in poison ivy with larger leaves and more potent urushiol.

“Leaves of three, let it be. Vines with hair, beware!”

Poison in our midst

Driving on rural roads recently, you can’t miss what has been called one of “the deadliest plants in North America” — poison hemlock.

It’s impossible to overlook this plant now. It is 4-8 feet tall with impressive umbrella-shaped clusters of white flowers that grow taller than most other plants near it. It grows all over — in pastures, roadsides, ditches and stream banks.

Recently, I saw poison hemlock growing at the edge of driveways very near homes. Something that toxic almost in the front yard makes me uncomfortable.

The attractive look of this plant concerns me. It dominates the landscape and could easily attract children to take a closer look or, heaven forbid, take a taste. The leaves look similar to parsley, and the white flowers are inviting.

Like other nasties, poison hemlock is both very attractive but also highly toxic. According to OSU Extension, “All parts of the plant contain toxic substances that cause respiratory failure in humans and other animals if ingested.” The ancient Greeks used this plant to execute Socrates, the Greek philosopher, and cattle can die from eating just 300-500 grams of the plant material.

If you live near this pretty but very dangerous plant, especially if you have children, use caution and make sure everyone knows what it is. Check with OSU Extension about safe ways to eradicate the plant.

Herb Broda can be emailed at 4nature.notebook@gmail.com.