It’s a Real Chameleon
The adage “leaflets three, let it be” is an effective begin in identification. Except in uncommon, five-leaflet populations in Massachusetts and Texas, poison ivy’s leaflets are organized in threes. But the plant can in any other case be so morphologically variable that it confounds all however professional observers.
“Its plasticity is really crazy,” Ms. Pell mentioned. And that has led to distinctive-looking phenotypes in numerous areas being designated as native species.
She begs to vary. As a part of her lengthy collaboration with John D. Mitchell, honorary curator at New York Botanical Garden, Ms. Pell has been sorting it out. In their upcoming Anacardiaceae chapter, to be printed in 2022 as a part of the huge “Flora of North America” venture, they’ve decided that the majority of those should not distinct species, however fall into 5 sorts of T. radicans.
“We didn’t recognize some well-loved local species,” she mentioned. And no, that’s not sarcasm you hear. Taxonomists typically change into emotionally hooked up to a specific species retaining its stature within the systematic hierarchy — even when that species is poison ivy.
It could be a floor cowl, or shrubby, or a woody vine (known as a liana), reaching practically treelike proportions. Its leaves might be shiny or matte (even in the identical inhabitants), in numerous shades of inexperienced (or red-bronze, upon emergence), and so they differ in dimension and form, with margins from clean to toothed or deeply lobed.
“In one area in Quebec,” Ms. Pell mentioned, “it has straplike leaflets and looks like a fern. In the Southeast, I have seen leaflets as long and wide as my head, and elsewhere, often very close by, leaflets shorter than my thumb.”
On the East Coast, poison ivy is most frequently confused with field elder (Acer negundo), Virginia creeper (Parthenocissus quinquefolia) or a bramble like blackberry (Rubus). But field elder’s clusters of leaflets are organized reverse one another, alongside the primary stem, whereas poison ivy’s alternate. Mature Virginia creeper has 5 leaflets; its stems have tendrils with thick pads on the tip, however are lacking the reddish roots that always cowl poison ivy vines. And Rubus has spines, in contrast to poison ivy, which by no means does.