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FLORA: Be certain you know the difference!

By Ken Moore
Flora Columnist

As described in last week’s Flora, you want to avoid close contact with ornamental smooth sumac’s viney cousin, poison ivy, Rhus radicans. Some of you will be eager to know that taxonomists have recently upgraded the name to its earlier nomenclature, Toxicodendron radicans. It sounds like “Tox-e-co-den-dron rad-e-cans” and is certainly more fun to roll off your tongue than is ‘rus rad-e-cans.’ Toxicodendron means poisonous tree, a clear warning to keep one’s distance.

Leaves of three, let them be/Leaves of five, stay alive. Photo by Ken Moore

I continue to be surprised that, when guiding school groups at a local nature center, I encounter so many youngsters that cannot identify this common poisonous native vine. The earth guide’s first action is to help the kids distinguish between the not-to-touch poison ivy and the, usually growing nearby, innocent Virginia creeper.

Compare in the photo above the poison ivy compound leaf of three with the Virginia creeper palmately (like a hand) compound leaf of five leaflets. Contact with sap of poison ivy causes a serious rash for most folks, while Virginia creeper is harmless.

Poison ivy can make a ground-covering carpet in sun and shade, and when it finds a tree to climb, the hairy stems are easy to spot as dark wooly cords clinging tightly to the trunk. In contrast, when Virginia creeper climbs a tree, the mature stems are free of such wooly hairs. The little holdfasts of young creeper stems resemble multiple tree frog feet clinging to vertical surfaces.
Both poison ivy and Virginia creeper have beautiful orange-red fall color that becomes noticeable in the interior of many trees at summer’s end.

Tree-climbing poison ivy vines are dark and densely hairy. Photo by Ken Moore

At this time of year, you may spot the fleeting beauty of Virginia creeper berries turning dark blue on contrasting red stems. The berries of poison ivy are whitish and not very attractive.
The berries of both vines are important food for birds and other wildlife. Seeds of both are cleaned in the digestive tracts of birds and dropped everywhere. Appreciating the fall color and wildlife value of both vines, I am happy to welcome them in my wild landscape, allowing free reign to Virginia creeper, but trying to restrict poison ivy to the back edges, mostly beyond easy reach.

Virginia creeper’s official name, Parthenocissus quinguefolia, is even more melodious than poison ivy’s name. The genus name is derived from the Greek, parthenos – virgin – and cissos – ivy. Imagine a botanist naming this newly discovered “ivy” from the Virginia colony in honor of the “virgin” Queen Elizabeth I several hundred years ago. The species name, from the Latin, quinque – five – and folium – leaf – is purely descriptive of the vine’s five leaflets.

Beautiful Virginia creeper dark berries on red stems signal a tasty treat for birds. Photo by Ken Moore

Enjoy remembering the botanical name; it’s great fun to hear it roll off of your tongue. It sounds like “par-thee-no-siss-us quink-a-fo-lee-ah.” Now try saying the botanical names of both vines out loud and with a little practice, you’re armed to surprise your companions when you discover one or both on your next walk.

Virginia creeper vines climb via tiny holdfasts. Photo by Ken Moore

Email Ken Moore at flora@carrborocitizen.com.

Find previous Ken Moore Citizen columns at The Annotated Flora

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