Where are you located? Plant in question looks a lot like false lily of the valley, Maianthemum dilatatum. This is a native wildflower, and while an aggressive spreader, it is not considered invasive.

not lily of the valley?

Is it located all over or just that particular part of the lawn? Would it be possible for you to cover up the place with a black garbage bag or a dark tarp to cut off it's access to sunlight? That is a safe way to kill off the plant (and grass too). it will have to be covered up for at least a month to kill off all the roots effectively. Then just rake over the area and resod or reseed.

I'm in central CT. My wife just located more along the edges of our property in the back yard (photos show front yard). I first noticed it last year growing under a small line of pines that separate my property from my neighbor's. Since then it has spread in my direction, but not his. But his lawn is healthier and sunnier at that border than mine, so perhaps it is able to fight off any new competition. Until last year, my side of the border had a few smallish pines that kept the area where the incursion started almost always in the shade. Also, my wife pulled a few and said the leaves propagate from a spreading root system. But always a single leaf pops up, over and over again. Gardengal48, do you know if false lily of the valley spreads in this manner? Looking at pictures of false lily of the valley, I notice that the two lobes behind the stem are far more pronounced than in the leaves growing out of my lawn, but maybe mine aren't mature yet?

Ianna, thank you for your suggestion. That may work, but I'm wondering, if these guys spread underground, would a tarp be enough?

a canadian lily of the valley spreads in shady areas. Its really a garden plant gone wild.

Tarp works to stop the plants from getting sunlight and they get sunlight via their foliage. So that's one way of killing them off safely. -- you can also use a vinegar solution to spray the foliage as this can be absorbed into the roots and kill them. I really hesitate to use anything stronger like herbicides which lingers for a long time and can kill off surrounding plants. You need a targeted approach here and this is the only thing I can think of. I would also recommend - since you are doing the all out war approach, to dig a trench around the affected area so roots cannot jump into the healthier spots in the lawn or as you said, put in an edger.

last, I say, put a trench to prevent more invaders from your neighbor's side, I suggest using this trench method as a control. Making your own 'Wall of China' to prevent invaders.. LOL.

OK! Right plant, wrong species! That's why I asked where you were located. Maianthemum dilatatum is exclusive to the west coast. Wasn't aware there was an eastern version :-) And this is a wildflower - not necessarily a garden escapee.

The tarp could help but it will also smother the grass. And it is not that effective for plants that spread rhizomatously (via underground stems). The rhizomes just keep growing to where the tarp doesn't cover and then pop up. Depending on how shady the area is, you might just want to encourage it and skip the lawn. Lawn grasses are difficult to encourage to lush growth in very shady locations and a shade loving groundcover - like this - is often recommended as a suitable replacement.

Otherwise, containment would involve some sort of root barrier/edging at the edge of the lawn and some targeting herbicide applications. Any broadleaf weed killer for lawns should work well - the stuff can't tell between a 'weed' or any other type of broadleaved plant. Just spray individual leaves directly and be sure none gets on anything more valuable.

gardengal.. He already mentions the grass is already growing poorly in this location so not a problem if it dies in the process of suppressing the invasive. I'm from the east and I know this particular plant and I've seen how it can spread. Light suppression accompanied by a weak vinegar solution as safe herbicide plus trenching or edging to prevent spread is the best method I can suggest. Its more about controlling the invasives. Done repeatedly, it will kill off the plant.

lanna, it is no different in growth habit from the similar species we have here. Plants that spread rhizomatously do not respond particularly well to light suppression. That is one of the benefits of being a rhizomatous plant - it doesn't need light to proliferate because it moves underground. And household vinegar as an herbicide is only moderately effective and needs sunlight to accomplish its work. You get even less effectiveness if applied in shady areas.

The Maianthemum is a native wildflower so technically not an invasive species, although an aggressive spreader under right conditions.

In the spring our yard is covered with violets. Are they a problem no, as once they bloom I mow over them and they are not noticeable the rest of the year.

I have heard of Lily of the valley not the variety you mentioned. Is it possible like the violets enjoy them and treat the yard as they were not there the rest of the year.

gardengal. it does sunlight which is the reason it sends out foliage because otherwise, it won't need to send off leaves at all. It still gets sun as its not in a deep shaded area. Plus around this time of the year, the trees haven't fully foliated yet around here. Yes it does spread thru rhyzome and like grass, they can be suppressed it the way I mentioned - the three way approach, light herbicides, light suppression and containment. Its well worth the try to do this method.

kmuttle -- oh my violets.. these spread by seeds and grow by teeny bulbs. My poor cousins' yard is filled with these invaders which came from her neighbor. that's one invader I would simple treat by removing the entire yard of grass and earth by at least 2 inches in order to remove. She's resigned to having them in her yard no matter how she hates it.

OK - you obviously think you know best. I just do this stuff for a living.

ianna--Tenacity is listed for wild violet control, although it may take several applications to complete the kill.

It's not listed for Lily of the Valley or any relatives, but y'know what? I might try it anyway. It's not listed for globe thistle, either, but it's also the only herbicide that gives me decent control of the stuff in my gardens!

Make sure the lawn is compatible with Tenacity use, of course, but the OP's Connecticut lawn shouldn't have a problem.

over here where I am, we cannot use herbicides except the ones they labeled 'green,. But sure try it out.. see if anything is effective.

(I just happen work in a university and close to people who work in botany.. plus that I've been gardening for nearly 20 years. I also respect there are multiple approaches to a solution. )