It looks like Epipactis Helleborine.

Looks like Epipactus helleborine, which is considered a weedy to invasive non-native species.

Definitely a helleborine, as others have already pointed out. They pop up in my shady woodland garden every spring. They're a serious pain to remove, as they have very deep and extensive rhizomes that require a lot of effort to dig out completely. Any small piece left behind can easily re-sprout later.

Interesting.... I hadn't heard about that one and had to look it up. Now I need to go out and look at a plant I noticed in passing when out in the garden this morning.. As I walked down a path, out of the corner of my eye I saw something that made me think ‘I wonder what that is - I don’t recognize it..’. I was in my way to a particular spot so didn’t stop to look closely. What I saw when I looked up the info on the helleborine makes me think I need to go back out and take a closer look!

Ack! I'm 99% certain that is what my unknown plant is! I looked closely at it late this afternoon and it looks exactly like the one in this link. DH will be trying to dig it out tomorrow and looking to see if we can see more of them!

Thanks to the OP for posting this - and thanks to those who identified it!

‘The flowers look like little orchids.’

That’s because they are little orchids. Every time this one comes up, which it does frequently, I wonder why it’s quite rare and threatened here, where it’s native, yet invasive elsewhere.

Floral, we could also talk about english sparrows and starlings. :) Keep your British flora and fauna home.

floral - I wondered that too....

I did more research to try to find out how deep is deep since most sources just said the rhizome is deep. From one site I found that was a bit more specific, it said a meter deep! Not having a backhoe, it appears digging it out is not an option! Since Ontario banned 'cosmetic' use of horticultural chemicals, dosing it with Round-up is not an option either... So it looks like the best we can do is keep it cut down and never let it flower so it doesn't seed around. It was growing under a bridalwreath spirea that we cut down to the ground to rejuvenate. That's why we never noticed it until after the shrub branches were removed....

I've killed scores of these in my gardens this year. The roots are quite deep, and decidedly alien looking.

Both sparrows and starlings are declining across Europe, having previously been very common. We’d welcome them back with open arms.

I wish you could too.

Yeah English sparrows and starlings are ultra abundant here in southern Ontario. Starlings in particular are linked to the decline of our eastern bluebird.

Are you short on ivy and holly too? I could send you a cubic mile of those.... and I have always sort of liked this orchid despite its non-nativity here. I’ve never experienced it being “invasive” personally. in fact I’ve always hoped it would pop up in my garden somewhere... though I should prefer our native Epipactis gigantea!

We’re okay for Holly and Ivy, thank you all the same for the kind offer. Both are native, thriving and no trouble at all. They host a myriad other native species and they even have their own Christmas carol.

I’m curious about the antipathy to E helleborine. It’s obviously an alien but is it actually invasive in the sense that it ousts native species or destroys habitats?

I can't say for sure, because it won't even grow for me..down here. But I think it's just an aggressive spreader, but probably not habitat destroying.

It certainly wasn’t invasive in The Bay Area in California where I frequently saw it Between the redwoods. It just popped up here and there. Never en-masse, never crowding anything out. Just a little orchid to brighten one‘s day. The same can be said about Portland and Seattle. I’ve also never seen it out in the real wild in the PNW.

Yes: because the alien orchid doesn't make visibly dominating patches like ivy or close thickets like holly there is not an obvious appearance of exclusion. However a lot of native plants - including native orchids - have a small footprint also. How many of these aren't growing in millions of little spots across North America now because this real estate has recently become occupied by the Epipactis?

Here they never perennialize. I just find the odd plant here and there. I wish they were more common in their native habitat floral_uk.