MDC advises caution with poison ivy and oak

MDC advises caution with poison ivy and oak

Photo courtesy of Missouri Department of Conservation

As the Missouri Department of Conservation encourages area residents and tourists to get out and discover nature, words of caution are also being offered about plants that can be toxic to humans.

The most common is poison ivy. According to the Department of Conservation, it is a poisonous vine that climbs to a height of 60 feet, or climbs via aerial roots. Poison ivy sometimes appears as a low, upright shrub.

Poison ivy leaves are alternate and compound, with three leaflets that vary in size and shape. The central leaflet has a stem that is 1/2 inch to 1 3/4 inch long and is longer than the stems of the other two leaflets. Lateral leaflets have unequal sides. Posts take on different shapes and forms as the season progresses. They turn red, orange, or yellow in fall.

The stems on poison ivy are light brown and hairy with raised pores, and climb by aerial roots. Trail stems until they find support. When they lack support, they assume an upright, shrub-like posture with single stems.

Flowers on the plants begin to appear anytime between May and June with clusters 1 to 4 inches long on new growth of stems. The flowers are small, greenish-white, fragrant. Then, between August and November, the fruit ripens with berries in grape-like clusters, about a quarter inch across. The fruit is usually creamy white, waxy, ball-shaped and usually smooth.

Eastern poison oak is a closely related species found in low-nutrient, sandy or rocky soils, including prairies, dry upland forest openings, sandy meadows, sandy savannas, and roadsides. It is uncommon but restricted to the southern part of the Missouri Ozarks and the northern part of the Bothell Lowlands. Poison oak does not climb or produce aerial roots, and its leaflets usually have three to seven deep, relatively rounded lobes. The leaflets resemble the leaves of white oak or black oak, and the berry-like fruits have indistinct bristles.

There is another plant known as poison sumac. Although some have used this name for the Missouri species, poison sumac technically belongs to a plant that is not found in Missouri. True poison sumac has compound, feathery leaves that contain seven to 13 leaves. It occurs in swamps and swamps in the east and north of our state.

Missouri has three other plants that are often confused with poison ivy. Fragrant sumac has three-segmented leaves, but the terminal leaflet lacks the distinctive stem found in poison ivy, and the berries are reddish and fuzzy. Elderberries have leaves of three to seven leaflets, but the leaves are opposite each other on the stem instead of alternating as in poison ivy. Virginia creeper climbs like poison ivy, but it usually has five leaflets instead of three, and it has blue berries.

For more information about poison ivy and other things you can discover in Missouri’s nature, visit

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