We did not plant green onions but they have prospered in our yard. We do our best to dig up the bulbs, instead of pulling the stalk from the ground, yet they continue to multiply. They look grass-like in our borders, thus making our borders look unweeded. This has been a battle for the 3 decades we have lived on this property. Last year, we were feeling fairly victorious in our battle with it. This year, there has been a massive increase. There is as much green onion as there is grass in our yard.
Washington County Oregon weeds
Thank you for your question. I wonder if you could pull one or two out, and take a photo of the entire plant--bulb, roots and all--and attach it to a reply. There are many members of the allium family, and some of them are considered invasive. Wild garlic is one of those, described here: http://oregonstate.edu/dept/nursery-weeds/feature_articles/wild_garlic_email/wild_garlic.html