Several nasty weeds seem to be appearing everywhere, apparently flourishing in spite of our heavy spring and summer rains. Poison hemlock and wild parsnip are unfortunately in full glory right now along with the more insidious poison ivy. Do you know how to identify these plants?
Poison ivy is considered a native, woody perennial, reproducing by seeds and rootstock. Most of us know that poison ivy has three leaves and are familiar with it as a low shrub, but many are unaware that poison ivy can wind its way up a tree. Look for “hairy” roots that help the vine cling to the tree or other support. People can sometimes mistake poison ivy for other plants such as wild grapevine and Virginia creeper, a mistake that can have negative consequences. A chemical called urushiol is present in the sap of poison ivy which causes the highly irritating rash, blisters, and itching in humans. Humans can become exposed to the sap through direct contact with the plant, indirect contact such as touching tools, livestock, pets, or clothing that have urushiol on them, and inhalation of particles containing the oil from burning plants. The Centers for Disease Control and Prevention is an excellent source of information at www.cdc.gov/niosh/topics/plants/exposure.html. Weirdly, poison ivy has considerable wildlife value. Small mammals and deer browse on the foliage, twigs, and berries. The white, waxy berries are popular food for songbirds, especially in winter when other foods are scarce.
Poison hemlock and wild parsnip are biennials and are part of the parsley family Umbelliferae, characterized by the shape of their flowers which look like umbrellas. Both have a fleshy parsnip-like taproot. Several other plants are often confused with poison hemlock and wild parsnip such as angelica (native), cow parsnip (native), and Queen Anne’s lace (nonnative).
Poison hemlock is poisonous, and all parts should be considered dangerous! It is very toxic. Sheep, cattle, swine, horses, and other domestic animals are poisoned by eating small amounts of green or dried plant material. It is also extremely poisonous to humans. According to Wildflowers of Ohio, this plant is what was used to kill the Greek philosopher, Socrates. It can be found along roadsides, fences, ditches, abandoned sites, pastures and railroads. The plant spreads along highways because there is constant movement that scatters the seeds. The stems can grow up to 10 feet and are smooth with purplish spots and blotches. The flowers are white, and the leaves are large, finely divided, and toothed, giving a lacy appearance.
Like poison hemlock, wild parsnip is a nonnative Eurasian weed. It can be found in many of the same locations as poison hemlock except that it is shade intolerant. Wild parsnip grows up to 5 feet in height with leaves that resemble celery. The stems are hollow, deeply grooved, hairy, and topped by hundreds of yellow umbellate flowers. If the plant juices come in contact with skin in the presence of sunlight, a painful rash and/or blistering can occur, as well as skin discoloration that can last for several months.
For timely information on all kinds of Ohio growing conditions, pests, diseases, and cultural problems, visit Ohio State University Extension’s Buckeye Yard and Garden onLine at email@example.com. You can search using keywords, or sign up for a weekly newsletter delivered by email. A recent post from June 21 titled, “Poison Hemlock and Wild Parsnip are going to Seed in Southern Ohio,” contains 19 photographs to help you stay clear of these plants so you can enjoy the outdoors safely.
Remember to visit the Delaware Soil and Water Conservation District’s website (soilandwater.co.delaware.oh.us) and Facebook page for all the details on our free drive-it-yourself Farm Tour on Saturday, July 20. We hope to see you there.
Bonnie Dailey is deputy director of the Delaware Soil & Water Conservation District. For information, go to www.soilandwater.co.delaware.oh.us.