By Kathleen Cue, Nebraska Extension Horticulture Educator (Week of September 14, 2020)
Identifying poison ivy can be perplexing, mostly because the leaves can look different from one plant to another. There is some variation in how the plant grows, too, with it sometimes looking like a groundcover, other times a shrub, and still others a vine. Those not familiar with the variations in the plant can have irritating results when hiking through thickets and stands of trees. The only thing consistent about the appearance of poison ivy is referenced in the adage “leaflets of three, leave them be”. From there, the appearance varies greatly from plant to plant. The term “ivy” indicates the plant is a vine, but a clump of poison ivy growing on the edge of my gravel road has the look of a groundcover, reaching just 6 inches in height. The vining characteristics of poison ivy do not become apparent unless there is something for the plant to climb, like a nearby tree, shrub or fence. Small hair-like structures on the stem, known as aerial roots, are the mechanism for poison ivy to gain a toehold in the smallest of cracks and begin climbing. Leaflet edges can have large serrations with the two outside leaflets resembling a pointed mitten and the central leaflet looking like a mitten with two thumbs. Occasionally, poison ivy will have no serrations on leaflets, a confusing thing indeed, but a quick check of the leaf arrangement and poison ivy will have leaves arranged alternately along the stem. Boxelder seedlings can look amazingly like poison ivy but the leaf arrangement will be opposite instead.
Poison oak resembles poison ivy, with the leaflets arranged in threes but it differs in that the leaflets are lobed, not pointed, and will resemble oak leaves. The real question of poison oak is does it grow here? It’s not likely, since the furthest north it grows in the Midwest is Kansas and Missouri. There may be pocket microclimates where poison oak overwinters in sheltered locations, but the plant doesn’t naturally occur this far north, so any stands of poison oak that might exist will be small in comparison to the robust winter-hardy stands of poison ivy found around here.
The misery-causing component of poison ivy, called urushiol, is persistent and exists in all parts of the plant. A brush killer is best for controlling poison ivy, utilizing a paint brush to apply the herbicide when desirable plants are nearby. Personal protective equipment keeps the applicator safe from the herbicide and the urushiol.