Leaves heart shaped, single per node, rotating roughly in 3 directions ( looks like star from the top )
Superficially resembles nettle as far as leaves shape and texture, though it's not ( no sting - checked ).
Flowers - not sure at this point.

Looks like Lunaria.
Money Plant (Lunaria annua)

Thanks, but doesn't look like it.. I see difference in leaves, no such tall stem, and I don't recall such interesting flowers / seed pods in mine..
Probably something more mundane..
Hopefully it flowers soon.

Yes I can see that there is no stipule so it cant be Lunaria. It does look as if it will flower very soon. Oops I meant no petiole.

Lamium? It does seem rather tall though. It certainly looks like one of the mint family though.

Yep, there's hope for some flowering, though it could take a while.

Lamium - doesn't look like it, Lamium has leaf nodes in opposite pairs, rotated 90deg between pairs from the look of it..
Ditto for mint, at least that I could see.
Checked for smell - no discernible smell that would resemble any aromatic herb.

It grows mixed up with peppermint here ( some can be seen in photos ), but it's different.

Thanks !

p.s. Leaving this on the backburner.. will gradually collect and post more info on next stages - more developed plant, flowers, seed pods, roots, then revisit / retry searching..

Found a pic of this flowering from last year.. or shall I say bellflowering ?
Now I remember those distinctive vertical clusters of ( mostly purple ) flowers, and later those ball-like seed pods..
Coincidentally, some specimens just got ready to flower too. ( apparently white too )








Another possible identification attempt ?
The thread "Plant identification" in Plant ID forum

This one finally provided a lead ( though probably different subtype )
The thread "What did I germinate?" in Plant ID forum

Bellflower ( Campanula ) - exact subtype to be determined ( there are lots ), but even so, it now has the desired identity.

Campanula?

kniphofia said:Campanula?

Looks like it. One exmple that grows in Ontario:

Look good for Creeping Bellflower (Campanula rapunculoides), that should nail it with the subtype.
( i actually hit that when flipping through some of subtypes, but I guess thumbnail threw me off so I skipped over it )

And yeah, as seen first hand and written elsewhere, it can be quite a pest, this one has been popping up all over the place.. gonna have to restrain it.

Good to know exactly what you're dealing with !

It's something of a thug but one year here it popped up among some creamy-lemon daylilies. It was a gorgeous combination!

This Campanula is freaking insane ! Here's one growing from a crack between concrete and paver stone pad under AC fan .. There's literally nothing, just a pinch of dirt. Talk about resilient. ( and thug )
( granted, it's looking a bit sickly, but it's grown this much.. )
( " who needs soil anyway, look i can grow without it " )

Not to mention in every flower bed, lawn.. So infestation has already happened, I'm guessing this goes way back.. Now I'll just need to thin it out, which is easier now that I know what I'm dealing with - the usual - prevent seeding, knock out plants, and I'll get a good grasp on that morphed first year stage too, I think I'm seeing a good number of those too.

I'm not worried.. We'll see who is a bigger thug.