If Plants Could Talk, These Should Say, “Don’t Touch Me!”

Many of us love nature and walking through the woods or other natural areas. But what potential dangers are lurking in some of the plants? Let’s review some of the “don’t touch me” plants and the potential dangers they pose to people. Note that the first four I mention literally have “poison” in their name.

Poison ivy

Perhaps the most common and best-known “don’t touch me” plant is poison ivy. It can cause blotching of the skin, burning water blisters, pain, and intense itching. Symptoms may appear quickly or within a few days.

Poison ivy is a 3-leaved plant. More accurately, each leaf is composed of three leaflets. This botanical characteristic prompted the saying, “Leaves of three, let it be.” It looks a lot like the leaves of the boxelder tree, making young boxelder seedlings and young poison ivy vines difficult to tell apart. However, poison ivy leaves are arranged alternately on stems, while boxelder leaves are arranged oppositely. Poison ivy also has a vining habit over time – climbing and attaching to tree trunks or whatever is nearby.

All parts of the plant contain and secrete a nonvolatile oil called urushiol (oleoresin), which affects the skin. The oil is not soluble in water, so washing with water alone does no good and may spread the oil. Washing with a strong alkali soap is more effective, especially if done soon after exposure.

Don’t burn poison ivy after it has been cut or grubbed out and dried. The smoke from burning the plant contains particles that can cause serious injury to the eyes, skin, and respiratory tract.

A real mystery of nature is that some birds will eat poison ivy fruit (a greenish white, smooth berry) without any complications (and then replant it elsewhere, with natural fertilizer added). Deer can also munch on poison ivy twigs.

Poison oak

Poison oak is a low-growing, non-climbing shrub with three leaflets, much like poison ivy. Although there have been unconfirmed reports of poison oak, it is not known to occur naturally in Indiana. Atlantic poison oak has been confirmed primarily in states to our south and along the Atlantic Coast as far north as New Jersey, so be vigilant if traveling to and hiking in these areas.

Poison sumac

A rare plant, poison sumac is generally found in or near wet areas and swamps. It can be about 6-20 feet tall, with compound leaves that have 7-13 leaflets and smooth margins (edges). Hairless green berries turn gray-white when mature. So, if you see a sumac with hairy berries or berries with a red to crimson color, it is more likely a non-toxic sumac, and may even be suitable for certain areas in home landscapes.

Poison hemlock

Poison hemlock is a weed that has become more prevalent in recent years. Poison hemlock looks a lot like wild carrot, a.k.a. Queen Anne’s Lace. They have similar flowers and leaves. Poison hemlock has purple blotches on stout, smooth, hairless stems. Conversely, wild carrot has hairy, ridged, and yellowish-green stems without purple blotches.

The greatest risk from poison hemlock is ingestion. Lethal doses are relatively small, so animal owners or parents of young children should identify it in their area and remove it if possible. Toxins can also be absorbed through the skin and lungs, so wear gloves and a mask when handling these plants during eradication efforts.

Plants that are often confused with “don’t touch me” plants

Fragrant sumac and Virginia creeper are both non-poisonous. Fragrant sumac has pubescent (hairy or fuzzy) leaves and red fruit. Virginia creeper, also called woodbine, is a common native vine present throughout Indiana. It has five leaflets. Young Boston ivy leaves have three leaflets, while the mature leaves are 3-lobed, but not separated as leaflets.

Other plants to avoid or be cautious around include cow parsnip, giant hogweed, stinging nettle, and spurges.

For further information, find Purdue Extension’s publications on poison ivy and poison hemlock at the Purdue Education Store. See also the Purdue Extension publication, “The Don’t Touch Me Plants,” under the “weed biology and management” accordion ribbon at the Purdue Weed Science website.