Poison Ivy or Poison Oak?

poison oak or ivy?

In the southeast part of the US, we have both poison ivy and eastern poison oak. But they are pretty hard to tell apart. I was taken to a site in the sandy southern part of New Jersey by a top botanist who grew up there. When he first showed me a plant and said it was poison oak I said "No, that's poison ivy." So he took me further and found a plant with big berries on it. And that was clear: the berries of eastern poison oak are much bigger than poison ivy berries, and also FUZZY!

In California there seems to be only Pacific poison oak. But Pacific poison oak often looks just like eastern poison ivy: it has leaves of three, grows as a vine or sometimes a shrub, climbs and also grows on the ground. The only sure thing is that eastern poison ivy has hairy roots that attach it to things when it climbs, whereas Pacific poison oak has clunky fingers to hold it to what it climbs.

There could be some western poison ivy in parts of California; I have seen it in eastern Washington. But how would you know? The four plants really can look similar.

I have another botanist friend who suspects they might all four be the same plant just adapting to the climate and soil by growing differently. Have to get some DNA testing going here.

Just for accuracy I better give those Latin names:

  • Eastern Poison Ivy = Toxicodendron radicans
  • Western Poison ivy = Toxicodendron rydbergii
  • Atlantic Poison Oak = Toxicodendron pubescens
  • Pacific Poison Oak = Toxicodendron diversilobum
  • Poison Sumac = Toxicodendron vernix

 

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