The Blog

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.

TAGS: Jelesko, 5-leaf
April 13, 2018 - 11:47am
LARGE poison ivy

As spring rolls around, poison ivy is one of the first plants to emerge. Spring leaves are usually red, but many new leaves are red, so that's not enough to go on. See our ALWAYS-NEVER criteria for deciding if a plant is poison ivy.

March 28, 2018 - 11:22am
poison ivy stump

When you cut down a tree, the sudden presence of sunlight encourages poison ivy vines to grow into the gap.

Here is a stump where the  white snow highlights how the vines, with nowhere to climb, start reaching in all directions, looking for something else to climb up.

TAGS: stump, winter
March 14, 2018 - 9:39pm
poison ivy barn

I had appeared on local media, talking about my favorite topic: poison ivy. After the show, a fellow contacted me to tell me about an abandoned barn in New Hampshire that he said I had to see.

February 23, 2018 - 5:15pm
poison ivy in winter

When poison ivy climbs it grows thousands of tiny red root hairs to attach to the tree, wall, or other vertical surface.

TAGS: winter
December 22, 2017 - 11:11am

When the leaves fall, many trees, fences, and buildings are revealed to be covered with masses of poison ivy vines. See how this very aggressive vine covers not only the poor tree, but also layers of other poison ivy, all scrambling upward in a nasty competition.

TAGS: winter
November 27, 2017 - 11:08am
Anne F in with knotweed

A research paper has just been published about the difficult invasive weed, Japanese knotweed. Seems that in some kinds of forests, this weed is taking over the understory and preventing new tree saplings from growing, thus threatening the future of these forests. 

November 15, 2017 - 5:53pm
fall poison ivy

Up here in central New England, 2017 has had an extremely late first frost. (I wil forgo discussion of global warming to avoid the hate mail that such topics generate.) 

November 11, 2017 - 6:46pm
Virginia Creeper in Turin, Italy

I knew without getting close that this red vine was NOT poison ivy. How did I know for sure?

Because I took this photo in Turn, Italy, and there is no poision ivy in Italy, nor anywhere in Europe, for that matter.

October 13, 2017 - 5:06pm
John Jelesko Lab, the Itchy Project

Watch this short video and consider a donation to help the Itchy Project!

October 1, 2017 - 7:39pm

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