Poison Ivy

If you only learn to identify one plant… this is the one.

Photo copyright Lauretta Jones

As a young girl growing up in a suburb of Cleveland, Ohio, my introduction to the natural world was limited to random invasive species in empty lots and bright, sticky petunias in tidy planting beds. Weekend visits to my cousins in the “country” seemed to me exotic adventure. On one of those visits, I was witness to the suffering of my eldest cousin who was solidly covered with itchy red sores over his arms, legs, and his distinctly unhappy face. In those days, we all knew the symptoms of measles, chicken pox, and mumps, but here was something different. That was the day I received my first formal lesson in plant identification: my cousin’s misery, I learned, was due to an encounter with poison ivy.

If you learn to identify just one plant, poison ivy (Toxicodendron radicans) is the one to spend your time on. Not everyone is vulnerable to its poisonous oils, but suffering a reaction is not a reasonable way to learn if you are one of the unlucky ones. As sensitivity can build up over time, having never had a reaction does not guarantee you never will.

Poison ivy – not actually an ivy – is a native plant related to poison oak and poison sumac. Its white berries form an important food for many birds. It thrives at the sunny edges of forests and in fields. As we continue to cut our forests into small, fragmented pieces, we unwittingly create perfect habitat for poison ivy to establish itself and spread.

Photo copyright Lauretta Jones

Poison ivy shows substantial variability in how it grows and what its leaves look like. Nonetheless, learning these basic characteristics will help keep you safe:

  • “Leaves of three, let it be.” You may have heard this mnemonic rhyme. Poison ivy does indeed have leaflets in groups of three (as do other plants, of course). Each poison ivy leaflet is shaped like a fat almond. Some leaflets may have several uneven teeth of differing sizes along their edges, while others on the same plant have smooth edges. New leaflets often emerge red-tinged and shiny in the spring, later turning standard plant green. In the fall, the leaves take on beautiful hues of yellow, orange, and red, but resist adding them to your autumn leaf collection.
  • “Hairy vine, no friend of mine,” is another useful rhyme. Poison ivy is a strong climber of trees, and often you might notice its densely hairy root pressed around the trunk of a tree before you are aware of the vine’s branches reaching out toward you, holding their green leaflets in your way.

I think of poison ivy as a stealth plant as it can appear to take on many habits. A plant’s habit is its typical shape or mode of growth. For instance some plants are trees while others grow as shrubs or vines. Poison ivy can be found in many guises. It can grow as  a low-lying ground cover where it seems to specialize in working its way up to the edge of a path. (This is another reason why it is prudent to stay on the trails.) It can appear as a meter-tall shrub. And once it finds a tree to climb, it can extend its branches quite a distance from the trunk and – to the untrained eye – mimic the innocent foliage of a tree.

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