What visual clues am I unconsciously using to differentiate these two species? (boxelder versus poison ivy)

I am presently at a friend’s house helping them attack the poison ivy growing in the backyard of where they just moved to, and I recall an exchange that I had with a friend a few years ago concerning poison ivy and boxelder. This was the picture I sent him:

“In an instant I recognize the one is a poison ivy sprout and the other a boxelder sapling, but I don’t have an awareness of what it is that I am subconsciously using to differentiate between the two. The leaves are both serrated, in groups of three, often with red stems, and a similar growth habit. The colors are slightly different, and after thinking about it the leaves on the poison ivy droop more, but apart from that and the very slight difference in the serrations, I do not understand how it is that I am so skilled in discretion between the two species.”

Crew, help me out. Are you able to discern which one is which? Please explain to me how it is that I can easily tell the difference between the two plants but cannot tell you why.

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I attribute that type of knowledge/awareness to time in the woods. I can ID poison ivy growing in ditches at 65 mph as I’m driving. My wife still struggles to see it 2’ away as she’s looking for morels or wild asparagus.

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I believe Poison Ivy is alternate budding while box elder is opposite budding. Poison ivy has the appearance of reaching out to touch you. Only young box elder seedlings have only 3 leaflets.

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There’s a “softness” to the box elder leaves. They seem crinklier, while the poison ivy leaves look more solid and glossy. It’s definitely hard to put in words, but I think leaf texture is the big difference here that you notice subconsciously.

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@swincher, I think that you are absolutely correct with that statement. I am looking at an incidence I just ran across where a poison ivy sprout is growing from beneath a boxelder sapling, and the boxelder leaf does strike me as being more delicate in appearance.

When I pull back the canopy of the sapling it is easier to see that there are indeed two species growing beside of each other.

I bow in humble supplication. You must teach me this skill!

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I experience that too. I call it “having eyes” for a certain plant. As you get familiar with one, I find you’ll begin to notice subtle cues about its form. Trees have distinct branching patterns and silhouettes, for example. The buds and bud scars are also distinct and recognizable up close. It’s something that comes with time, though in my experience not everyone develops that skill. I think you have to be observant by nature and attuned to details. Some dont have that propensity

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I find this to be absolutely true, and it aids me greatly when determining the species of a tree, especially when it has no leaves or it’s bark greatly resembles another tree that grows in the same geographic area.

This as well. I’ve worked with people who didn’t have the ability to differentiate between species based solely on their growth habit. I am glad to be blessed with it.

And now I’m starting to itch… :grin:

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It’s pretty easy around here. P.I. grows in “patches” in this area and looks like nothing else (to my eyes). It’s a different color green than most other stuff growing in the ditches too. Of course, I also used to be able to spot “ditch weed” at similar speeds/locations

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I discovered that poison ivy isn’t so bad for my body through two separate occurrences. The first one is how to wash when you have been exposed to urushiol (the oil that causes the reaction). I like to take it a step further than he suggests in this video: I use a Scotchbrite pad and Dawn liquid dish soap to scrub and exfoliate thoroughly. Done within about 8 to 12 hours of exposure it has been very effective.

The other discovery is how effective the hottest shower water is at making the itch go away for roughly 12 hours and allow me to sleep through the night. I don’t know the mechanism at work but it has helped me out tremendously on those rare occurrences I didn’t realize that there was a poison ivy vine buried in the English ivy covered tree trunk that I was working on. Turn the water heat up as high as you can stand it and cook the affected area for 30 seconds to a minute.

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Yes, I have experienced this phenomenon too. Like how you can tell prunus spp. blooms from Amalanchier spp. Even traveling 70 down the highway. I think humans may be tapping into their predator search image abilities when doing this sorta thing:

https://evolution.berkeley.edu/aloha-spider-style/the-predator-search-image-a-look-at-blue-jays/

https://scholar.google.com/scholar?hl=en&as_sdt=0%2C20&q=predator+search+image&oq=predator+search

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PI leaves are a bit darker green and the vein in the PI leaf is a bit lighter than the leaf… enough that the PI leaf vein stands out more.

BE leaves are a bit lighter green and the veins basically match the leaf color… so they do not stand out as much.

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Most ginseng hunters experience this…

When you have been on a long seng hunt… scanning the hillsides for that specific leaf pattern for hours…

After you get home, take a shower… the rest of the day… almost every time you blink your eyes… or if you turn your head quickly to look at something … the fridge, a wall … or a door…

You see ginseng leaf patterns that are not there.

That normally stops after sleeping.

TNHunter

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The ~1 acre property of the first house that my (now ex) wife and I owned had not been kept up very well by the previous owners. I set about destroying the poison ivy that was all through the woods, and under the right sunlight conditions, this stuff thrives in Georgia. It took several hours to get it all, and when I lay down for the night I discovered that when I closed my eyes I was seeing ghost images of the distinctive poison ivy leaf shape.

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I cut down a couple hundred oak, hickory, sourwood, etc… trees back in January… clearing land for our new home site.

I have been cutting those up into firewood… and from handling that wood… i have some PI now on my right hand and arm.

Yep you can get it from the dormant vine alone… leaves not required.

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Yessir, and never ever burn any part of poison ivy.

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Never mow it or weedwack it either.

I use to do poison ivy removal as a side job. ALWAYS brought on the job a bottle of rubbing alcohol with a sprayer top on it. Occasionally spray down my tool handles, gloves, pant legs, and boots.
Rubbing alcohol neutralizes the urushiol.

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In addition to the things others have said, the angle of the base of the leaflets to the stem is different in boxelder. But i think mostly i notice the color of pi, and the glossiness of the leaves, and the robustness of the leaves. And yes, the are alternate, not opposite, on the vine which never turns into a trunk.

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There might be an alternate of poison ivy which has leaf arrangements in a different configuration, but if you examine the pictures that I’ve posted their leaves are arranged opposite each other, not in alternating fashion.

As I was reexamining those aforementioned pictures just now I had a bit of a “doh” moment! I realized that on the boxelder, those leaves which are opposite each other do actually point away from each other in completely opposite directions, whereas the opposite leaves on the poison ivy trend slightly towards the tip of the leaf on the end which is between them.

The leaflets on a single leaf are opposite. But the poison ivy leaves (each of which has three leaflets) are alternate on the vine. Whereas boxelder is a maple, and grows opposite leaves (each with three leaflets when young) on the twigs.

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