The Mystery of 5-Leaf Poison Ivy

5-leafed poison ivy

It has been an absolute rule for over a century: "Leaves of three, let them be." 

Poison ivy has only three leaves (actually leaflets) in a group. And that is still true about 99.9999% of the time.

But last summer, an alert cyclist noticed three places in the western suburbs of Boston where the poison ivy ground vine had an extra pair of leaves. 

This is rather big news for poison ivy science, and we don't yet know what it means. But we sent samples to the John Jelesko, who is Associate Professor of Plant Pathology at Virginia Tech. John is one of the nations leading poison ivy science researchers.

He planted some of our local Boston area vines and when they leafed out this spring in his lab, SOME of the stalks had 3 leaflet, some had 5. Again, we don't know yet what this means, nor how one plant could have both kinds of leaves.

The big question is whether this variation will spread, or remain very very rare. We assume, for now, that this plant has the same itch-producing oil as the normal ones.

Here is contact information for Prof. Jelesko's lab, where they are looking for citizen scientists to get involved and help gather poison ivy data for research:



Citizen Science Project Website:

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