There's several kinds of stinging nettle, they aren't all the same...
The nettles I'm familiar with have alternate leaves, that plant has opposite...
One type is small and light colored and grows in open disturbed ground- field nettle
The other only grows along creek banks and adjacent damp wooded areas it gets large and is deep green
-- creek nettle!
Creek nettle are no joke! They will light you up!
By midsummer they can get head high, they're hard to spot then and it easy to find yourself fully surrounded!
If you in short pants and sleeves... Your in for a rough ride! God forbid your shirtless!
From here down I'm talking about creek nettle.
When I'm walking the woods I notice a plant that looks basically just like the plant above, for a while I misidentified it as nettle... That is, until the real nettles get right and start stinging!
They grow side by side here and really do look similar!
In addition to the leaves being alternate vs opposite, I notice that it has a more "aggressive" look to it(imagine that!)The serrations on the leaf are sharper, especially the point of the leaf, not rounded at all, the point often curved off to one side.
The leaves will be more broad at the midpoint, slightly more rounded except for that long tip.
The leaves will also be darker green in the middle, and light around the margin, the youngest leaf will almost always have a portion in the middle that is very textured, bumpy, pitted, I'm not sure exactly how to describe it.
Close inspection will reveal the nasty stingers, they will often be very long and dense toward the crown, looking like gramps needs a shave... If you get them in the sun, the stringers will make prisms and flash all the colors or the rainbow... There's beauty in everything!
Nettle will also have purple towards the base of the plant.
The best give away to my eyes as I'm walking and tiptoeing through these 2 plants, is that the nettles terminal shoot will have a section at the very top that has a lot of leaves very tightly packed, as the plants grows they stretch but the top always has a thick canopy and sparsely leaved lower section.
Think palm tree...
Once you train your eye it's unmistakeable! But until then... there's many imposters...
If you do get hit by em, don't scratch!
And just remember to breathe!
You know there's one fail safe way to figure out if the plant you're lookin at is a nettle!