17 July 2009

An improbable poison ivy

Lately I have been making frequent trips to Georgetown University Hospital in Washington, D.C. due to my wife's illness (details some other time). While walking along a wall at a busy section of the hospital yesterday, I noticed a lone plant growing out of a crack at the base of a brick wall.


It was a young poison ivy.


I have been noticing more and more poison ivy plants around this summer. Either I have become more aware of them or they are turning into a more aggressive plant and spreading themselves better. Could the climate change have something to do with that?


Anonymous said...

Hi Aydin,

This is not poison ivy, it is a baby plant of Virginia Creeper, which often grows on buildings, as does its relative Boston Ivy. They are both in the grape family. Neither are at all closely related to true ivy.

When Virginia creeper is very young like this, it has only 3 leaflets; when it gets a bit bigger it has 5 leaflets. I pull the baby ones out of the plantings outside my building in NYC all of the time. It is a common weed here.

All best wishes to you and to your wife,

Susan J. Hewitt


That is poison ivy.

Virginia creeper has 3-leaflet leaves only when it is very young & small. And even then, there are mixed leaves, some with 3-leaflets, some with 4 & slightly larger ones with 5 leaflets. In comparison, the plant that is the subject of this post had only 3-leaf units & it wasn’t a very small plant.

Anonymous said...

OK I guess I am wrong. I apologize Aydin. The young VC plants I get in my garden are all 3-leaved, and don’t change over to 5 leaves until they are quite tall. I guess it is a variable thing.

You saw the plant itself and I only saw a photo. You know how hard it can be to ID something from a photo. I expect it had the glossy leaves of poison ivy, which are a brighter green, whereas Virginia creeper is not shiny at all and a duller darker green. Also you have the scale of it clear in your mind, whereas I don’t know how big the plant was really, as bricks vary somewhat in size (or at least they do in this town.)

Sorry again,




Corrections are always welcome.

xoggoth said...

At least we don't have that in the UK although we do have stinging nettles.

Hope the missus is ok, mine's a bit poorly at mo too with this and that.

poisonivyguy said...

BTW, leaves of three, let it be

VIRGINIA CREEPER always has 5 leaves, this pic has 3 leaves

Anonymous said...

No need to wonder; poison ivy is proliferating because of increased CO2. You may not have seen the news items last year about the Duke University study. See:


poisonivyguy said...


Milder winters promise that poison ivy plants over winter better by surviving the cold. Because this weedy vine is a woody perennial, means not only does this plant now survive milder winters, but actually comes springtime this plant actually has a head start, it being the plant picks up growing from where it left off in year previous, was last autumn. There are poison ivy vines measuring 12 inches across in diameter, are now found growing up the sides of trees, these vines are some 65 plus years old.

Anonymous said...

There is some evidence (i've long forgotten the source) that poison ivy proliferates in higher C environments.

FWIW Poison Ivy has become obviously more abundant in Iowa over the past 30 years. I have no data, I can just tell. It's also more abundant in urban areas-I don't remember that from my youth.

Bassball_Batman said...

The "Greek Cross" 3 leaflets: lower "arm leaflets" spaced down the stem from the head leaf -- that's trademark of poison ivy/oak. The "Roman Cross" 3 leaflets: all three leaves almost bunched up together atop the stem -- trademark of Virginia creeper. The ones in the picture look spaced apart -- gotta be poison ivy.