The Intruder: What's This?

Nobody knows. It is an annoying plant.

It spreads like quack-grass with running roots. Lots of roots. The smallest piece of stringy root will grow a new plant. It has a  herb-like smell vaguely  reminiscent of wild celery, but is not wild celery. I seem to be mildly allergic to it.  This innocuous-looking plant  is pretty enough.

It might be a weird variety of nettle. That's what our favourite gardening zeitgeist Glory Lennon suggested. It has no hairs on the stem,  and seemingly, no any attack equipment built in. Well, unless you count 'invasive'  and  'pretty enough', and then there's always  that herb-like smell vaguely reminiscent of wild celery. 

Here's a picture of the unidentified intruder.  You decide. If you do know positively what it is, please do let me know!

What is this plant?? All of the greenery  in the photo is the same species, hooked together by a complex root system.Notice it is growing around a double layer of old shag carpet placed in a failed attempt  to eliminate any new growth.

 The intruder is irritating to the skin and has proven almost impossible to get rid of.  It's on the north side of the house  and adjacent soil is moss-covered.

 It seems to like damp, cold soil.   This is what the root systems look like, the roots are fleshy, stringy, and tough. It spreads underground, out of sight,  and pops up everywhere just to annoy us.  If covered up, like in the above picture, it keeps growing underground until it is safe to pop up some more, just to annoy us.

The large, complicated root system spreads underground like invasive wild mint does

 Clearly this stuff spreads in the same manner wild mint and other invasive plants do  and  is capable invading and taking over an area --and pretty quickly.

 Here at Incoming Bytes I'm always looking for the bright side.  I'm hoping it's valuable or something!  
The area to the right has had most of the intruder removed but it will easily regrow within a season.  I'll be a major world producer of 'the intruder' by next year.   If I could have a dollar for each one of these plants, I would fill up the bank account in no time, don't you think so?.
Maybe not. It's virtually all hooked to the same root system. Does that mean it's really just one plant?  "That'd be one buck please."
One buck.    That figures.

The intruder spreads with a vengeance.

This intruder tops out at 12-14" in height.  We thought a lot about Glory's clever suggestion that it could be a sub-species of  nettles.

Glory does have a variety of height-challenged common stinging nettles,  that look like these:

Common Stinging Nettle

We too have common stinging nettles in this area, N.W. Ontario.  It is  the swamp kind  --but grows to about  4' tall or even higher, and by the majority,  they spread by seed.
Our  everyday Stinging nettles do look quite similar to these nettles but obviously a lot taller. They  pack a nasty welt that burns like agitated fire  if  a careless hiker accidentally rubs them across bare skin.

By the way, nettles are not all bad, you can harvest, dry, and use them for tea,  or pick the tender growth for cooked greens . Wear gloves if harvesting. Good thinking.  I digress.
  
What is the intruder?  Anyone know? Is it edible?  Does it have any uses that such as curing incurable diseases? Is it healthy or dangerous?  Will it take over N. Western Ontario by next Tuesday? 
I do hope readers here at Incoming Bytes can help resolve this question.  What is this intruder anyway?  I know I asked already, but I'm in a hurry.  Is it valuable?  I could use a buck.


Is that incoming I hear?