Leaflets Three, Let It Be…Maybe

About six summers ago I was walking up a narrow ravine in River Heights with two guys while evaluating erosion and landslide problems caused by the excess runoff from the rooftops and pavement of their neighborhood – which was strung out along the narrow ridgetops. In one place I was wading through a low shrub patch and they yelled at me to get out of the poison ivy. However, I was confident that it was actually a thicket of baby box elder trees, resprouted after being chewed down by deer. They wouldn’t believe me, and wouldn’t continue until I plucked a bouquet of leaves and chewed on it. In a similar ravine in Coralville, a homeowner showed me a patch of “real tall poison ivy” that he had been spraying beyond his back fence. It was actually bladdernut, complete with its little papery seedpods.

So today’s post is just to mention that there are four desirable native shrubby species around there that have three leaflets (see image). They all have different growth forms, different colors, and different fruits from poison ivy, but since the three leaflets seem to be the red flag which invites overreacting, let’s focus on these natives. (I didn’t illustrate Virginia creeper or woodbine because even through their viney growth forms very much resemble poison ivy, their mature leaves always have five leaflets. Occasionally their young leaves will temporarily show only three leaflets – just look at the older leaves to find five.)

• Fragrant sumac: At first glance, fragrant sumac gives me pause because it is rather closely related to poison oak and poison ivy, and does bear some family resemblance. It was especially common on the sand dunes in the northeast corner of Johnson County, associated with the Cedar River. In recent years, it has become quite popular as a landscaping shrub. Note the central leaflet, which has no separate petiole, while the central leaflet on poison ivy has a long, conspicuous petiole.
• Bladdernut: To me, bladdernut looks so much like young box elder that I’ve been several paces into a patch before recognizing my error. The spring flowers are tiny white bells, and in summer, once you note the little paper lanterns, you will be able to confirm that it is not poison ivy.
• Hoptree: Hoptree’s growth form bears no resemblance to poison ivy. It also often has some of last year’s paper disc seed wafers still attached.
• Box elder: Young box elder is never a vine, and usually has long, slender shoots as well as most leaflets in groups of five instead of three.

Poison ivy is the only one of the group with little aerial rootlets along the stem, the only one with a vine growth form, and the only one with clusters of waxy white berries in the autumn.
So before you go out to nuke that patch of alleged poison ivy in your yard, or fencerow, or woods, give it some careful scrutiny. It might not be the guilty party.

Note: the silhouettes illustrated were modified from photos in The Tree Identification Book and The Shrub Identification Book, both by George Symonds, and represent common leaf shapes and relative sizes.