Poison Ivy ID Quiz

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Identifying Poison Ivy

Poison ivy leaf shape. Two mittens on the sides giving a thumbs down with bilateral symmetry on middle leaflet.

I've posted in the past about poison ivy (1, 2, 3), but thought I'd post again, this time with an eye to identification. My goal with kiddos at Crow's Path programs is to get them to be able to subconsciously identify poison ivy while running around playing games. This definitely takes practice - lots of dirt time looking, drawing, studying - but once you create a search image and lock it into your brain you no longer have to think to activate that process. Awareness, to a certain degree, becomes a passive, embedded process.

My original post on poison ivy from so many years ago focused on the diversity of poison ivy, but also the general form. It's amazing to me that we can identify a species from a thousand different angles under a thousand different lightings. No two poison ivy plants are the same size, shape, color, texture. But the patterns are distinct enough that our brain can readily generalize a specific form and lump it in with other similar forms and parse it out from dissimilar forms.

Poison ivy with damage from a leaf miner

Researchers recently found the same process happens with ducklings, which immediately after hatching are able to imprint onto a mother figure. Imprinting isn't about recognizing a static form, like a circle or star, but rather a complex moving creature that will guide them to safety. The guide may be sneaking through tall grass, flapping their wings, or swimming across the surface of the water. Whatever their varied shape, a duckling's survival depends on its ability to recognize their alpha. So to do humans share an ability to recognize and lump, though as the ultimate generalist omnivores fortunately we lack the lazer like focus on a specific entity and instead have a far less specific and infinitely more powerful ID skillset. Being able to recognize many different forms translates to us being able to recognize and consume some 600 different genera in any one location (Carol Yoon describes this odd upper limit of 600 forms in her book on taxonomy Naming Nature, referring to a person's ability to name a max of about 600 different species, bands, products, etc from memory).

Forging a search image requires spending time looking closely (or I guess just subconsciously assimilating small bits of information over long periods of time works too as I don't ever remember learning to identify dandelion or pigeons or Katy Perry, but here I am capable of recognizing her almost instantly on a poster at Staples). As much as this can work, looking closely is more fun, more transferable, and more interesting. So, looking closely at poison ivy might reveal:

Stem

• A woody stem
• Each aerial stem typically has only 1-2 leaves emerging from it
• Alternate branched leaves
• Poison ivy that has taken to vining, at least in our region, is very uncommon
• When it does vine it uses aerial/adventitious roots to attach to tree (not tendrils, spiraling, or hooks)

Leaves

• The 3 leaves are actually 3 leaflets that together form one leaf. 
• Smooth (not waxy or hairy)
• Leaves often show signs of damage from leaf miners
• Form a T-shape, with two on side having short petioles (leaf attachments) than the middle leaflet
• Side leaflets are asymmetrical, middle one is bilaterally symmetrical
• Two side leaflets often look like they're given a thumbs down
• 
  

Flowers/fruits

• The fruits are like little whitish yellow pumpkins and readily pop off the stem
• They're often hidden beneath the leaves so difficult to find
• I've observed deer and catbirds eating them

Roots

• Reproduce mostly via runners (I've hand pulled poison ivy and if you get a runner you can pull up a few feet of horizontal roots!!)
• Roots are dark brown and around an 1/8"-1/4" in diameter at most.

Dichotomous key (VII.d) - The world of internodes cont'd (Adornment)

Adornment - thorny parts

A twig at its most basic form, is rather helpless against predators. Fortunately, trees do not leave them unaided. For example, sap can contain a range of chemical defenses (like the toxic orange sap of staghorn sumac) - this is particularly prominent later in spring when the sap gets, as they say in the sugaring world, buddy; I've written about that previously. Many plants, however, have figured out clever solutions by remolding different parts to serve a more spiky purpose; we only have a scant few trees in our area that have these spikes along their stems - though there are a number of delightfully delicious plants that have thorns (e.g. raspberry, blackberry, roses). These sharp projections derive from three different parts of the plant, the stem, leaves, or epidermis. Also good to remember that the terms below are botanical terms and are vernacularly often used interchangeably.

Chickadee flies from buckthorn branch

Spines are projections that form from the stem of the tree, arising from buds. In buckthorn, as shown above, they form at the tips of branches, or rather these spines are the tips of the branch. Hawthorn has very prevalent spines, as do honey locust and osage orange.

Thorns are modified stipules or leaves. The sharp projects on barberry and black locust, for example, are thorns. Above are the paired thorns of black locust, or pointed ears of Marrowzodufia Blugly the Dwarf, as you'll remember from my posting on bud scars.

Multi-flora rose thorn

Blackberry thorn with a scar just above it from where another thorn fell off

Prickles derive from the epidermis and are not vascularized (hence the can be popped off quite easily). Roses, raspberries, and blackberries all have prickles. Tracing the stem of a blackberry, rose, or raspberry, it is easy to find a number of scars dotting the stem from where thorns have fallen (or been ripped) off.

Tendril anchoring a grape vine to another twig. 

Showing adhesive pads on the ends of Virginia creeper

Adornment - clasping parts

Since vines put very little investment into their stem for structural support, and therefore need some mechanism by which they can cling to other objects as they wend their way up to the top of the canopy. Grape vines and Virginia creeper (both in the grape family, Vitaceae), have tendrils, which are highly specialized anatomical features for vining, originating from the stem. Virginia creeper, which is in the grape family Vitaceae, even has adhesive pads at the tips of the tendrils. 

Zoomed in view of a sharp and grippy bud of a bittersweet vine

Bittersweet climbing a sugar maple sapling

Tumurous growth of a sugar maple in response to a bittersweet vine

Other vines, like hardy kiwis and oriental bittersweet, accomplish this task with pointy buds that anchor the vine as it spirals and wraps around a substrate, often strangling and killing its unwilling host over several years. The constricting force around the stem of the tree being strangled cuts of circulation in new conductive tissue, effectively cutting off the host's supply chain. We also have a number of perennial herbaceous vines that encircle the substrate as they climb up it (e.g. deadly nightshade, morning glory, bindweeds, hops).

Poison ivy vine attached to white pine trunk. Image is from August 2012

Poison ivy vines have thousands of root hairs that anchor the stem to a surface. No other vine in our woods have this. This paper provides a good synthesis of different strategies of vining plants and unanswered questions concerning vines.

Poison ivy, yet again

What: The above is an amalgamation of 23 photos I took of poison ivy leaves last fall (the three leaves are actually leaflets and collectively form a single leaf). I then put the transparency of each image at 1/23 to get the final result. I got the idea from visual artist Jason Salavon.

Last year in my post I wrote about eating the young leaflets as they got bigger and bigger. This April I got a little rash on my wrist (same spot as 2 years ago) and so I decided to try the treatment again. I started as the leaves were first bursting open 2 weeks ago. Each day for a week I ate a tiny leaflet (progressively bigger, starting with a piece about half the size of my pinky nail). I then moved to about once every other day. Plants are less potent when they're young (why you harvest medicinals later on in their life cycles when they can put more energy into their chemical defenses). So as I developed a defense to the urutiol by ingesting the plant, the dosage was getting more and more concentrated as the leaves get older. It's probably too late to start this year if you're interested in this treatment, but maybe next year. And some people have much much worse reactions than I do so I would strongly suggest doing lots of your own research on folk remedies and this type of tolerance-development before trying on your own. You run a risk of having a severe systemic reaction.

Poison ivy

What: Above is an amalgamation of 23 photos I took of poison ivy leaves (the three leaves are actually leaflets and collectively form a single leaf). I then put the transparency of each image at 1/23 to get the final result. I got the idea from visual artist Jason Salavon. I've been really interested in the diversity within a species, particularly since everything at this time of year is so abundant. It started with toads (will post a series of photos of them) but turned to poison ivy.

Yesterday I was out with my UVM class, Natural History of Centennial Woods, and we were taking a closer look at poison ivy (Toxicodendron radicans). I'm not a big fan of the "leaves of three let it be" mantra as it prevents people from actually looking at the plant. Besides, strawberries have 3 leaves, as do boxelder, clovers, some Virginia creeper, sarsaparilla, and heaps of other delicious and beautiful plants.

To avoid confusion and cement an understanding of what poison ivy looks like, we created a list of features that would help us distinguish it from other plants. Here are some of the ones I can remember:

• Woody stem
• Three leaves
• Often has toothed edges to leaflets, rarely smooth (or entire)
• Fades to a dull yellow 
• Vines have "hairs" on them (see image below)
• Middle leaflet has longer petiole (what attaches leaflet to stem) than two side leaflets
• Middle leaflet symmetrical, lateral ones asymmetrical
• Two leaflets on side look like they're giving the thumbs down

Ecological notes: Also of note on the poison ivy leaves were an abundance of poison ivy leafminers (Cameraria guttifinitella) that appear to be eating the upper layer of cells on the leaves. A couple years ago I watched a catbird eat the berries from poison ivy with great relish. I've seen rabbits nibble leaves, and apparently plenty of other animals will eat the plant and be unaffected by urushiol, the toxic oil in the leaves, stem, and buds that cause us such great irritation. So just because you see an animal eat something doesn't mean you can (particularly don't try and learn which mushrooms to eat by watching red squirrels).

Where: Centennial Woods, and any moderately rich, well-drained but moist soil near you.

Jewelweed & Poison Ivy

What: I got poison ivy (Toxicodendron radicans), at least I think I did, this year for the first time ever. I know I've been exposed to it numerous times before so I was disappointed that I might have finally reacted. This year I thought I'd try what Eric Garza (http://path2resilience.com/) had mentioned to me a few years ago: nibbling a bit of the leaves to build up immunity. I started small, with a bit no bigger than my pinky nail. I waited a couple of days without reaction and nothing happened so I ate another one of the small leaves. That was two days ago and I'm still here. I'll try one more small leaf this year and see if I react to the plant again.

An old timey journal says that anything alkaline (or basic) will temporarily alleviate symptoms but does not grant long-term immunity to poison ivy (Dr WF Dieffenbach's "Treatment of Ivy Poisoning" in Southern California Practitioner v.29). The author describes his experience developing a strong adverse response to poison ivy, finding out about auto-lacto therapy (drinking milk of an animal that had grazed on the toxin), and testing the treatment with success. He fed a cow grass and poison ivy then consumed a pint a day for two days. That year he developed no further rashes. In following years he developed a rash again, indicating that immunity is not permanent and follow-up treatments are required. Admittedly the article is quaint in its anecdotalness (it was published in 1917), but warrants a closer look at treatments for ivy poisoning. **It is appropriate to note here that the plural of anecdote is not data. Also pertinent is that I'm not an apothecary, healer, or medical professional and I only recommend doing this after doing your own research/asking the plant itself.

Ecological notes: Centennial Woods is filled with poison ivy, as are most places that are wet, but well drained, and rich, but not excessively so. As is convenient with mugwort growing near poison oak out west (mugwort can be used as a poultice to treat the itchiness caused by urushiol in poison oak), here in New England jewelweed (Impatiens capensis and I. pallida) almost always grows near poison ivy (but the reverse is not true as poison ivy is much less common).

Where: The photos are from Centennial Woods. Below are a couple of look-alikes, at least in the early stages. On the left is sarsaparilla, which has 3-5 leaflets, doesn't have a woody stem, and splits into three branchlets. On the right Virginia creeper (Parthenocissus quinquefolia), which has suction like discs on the ends of their tendrils and five, not three leaflets.

Warning: While I've seen catbirds eat poison ivy berries with gusty, people should never eat older leaves or berries and definitely don't burn poison ivy. If you do try eating young leaves or milk from goats be extremely cautious. Only try exceedingly small amounts at first. And most importantly, do your own research. I'm quoting stuff that I found that proves what I want to believe, I'm sure there's a thousand other anecdotal sources out there that contradict what I've written.

Other notes: Poison ivy is in the same genus as other toxic plants like Poison sumac (T. vernix), poison oak (T. diversiloba out west and T. pubescens out east). The genus is in the Cashew family, Anacardiaceae, which also includes staghorn sumac (delicious) and, not surprisingly, cashews. Members of Toxicodendron are occasionally placed in Rhus, the same genus as staghorn sumac.