I don't think that would work. A neighbor had hers contained, set in the ground and it 'escaped' and has invaded the surroundings.

Lily of the valley does well beneath trees I've seen them beneath sugar maples which do suck up a lot of water so my guess is, it would probably do well under cedars as well.

I do have it though in an above ground cement container - which isn't working for me. I like to see it fill up the container but so far it hasn't done that. I'll let it be until next season - if it doesn't work then I have to chuck it out.

Lily of the valley is invasive. It took me 4 years of constant pulling to get rid of them in my flower bed. They spread by risomes under the ground. Much like quack or twitch grass. Under a tree might be all right but keep them out of your flower bed.

If you simply want some ground cover under the trees try Laminum. It will completely cover in around the trees. It's easy to dig out clumps to keep it in control, and the space will fill in fast. It has pretty mauve flowers in late spring and the leaves are white and green. I cut out pieces of mine and use it as fillers in pots too.

I have lamium everywhere and I love it. I also have lily of the valley and have a hard time getting it to spead. I wish it would grow faster and spread more.

Here is a link that might be useful: My Country DIY Blog

I agree on the lamium. they are in bloom right now - a really nice pink.

Funny, Sheryl - i have the same problem! My lily of the valley was planted years ago - ten, maybe? - and has been really slow to spread. I planted it at the back of a shade garden and left the side open hoping that it would spread out through the opening and down the incline towards the creek. It finally started doing that a couple of years ago. I got impatient, though, and actually planted some goutweed back there! I figure they can duke it out in their efforts to take over the world and we won't have to try to cut the grass on that slope. :)

Lily of the Valley is a real thug. It spreads through runners some 2 feet deep. I had it under a large sugar maple (it was here when we moved in 26 yrs. ago), cut the maple down and have been trying to get rid of it ever since. I have grown beans etc. in the space, but every year it is there. I had planted a few plants under an apple tree and it is tring to take over there. Be careful of the lamium though - I have three of them. One with white flowers, one with pink, and one with yellow. They are all in bloom now but the yellow one is invasive. I am also trying to get rid of it. It spreads much faster than the other two.
Northerner.

I have had the purple and pink lamium for years and love it. I don't find it invasive and it is so easy to pull up. I will watch for the yellow, though, and not plant it. Thank you for the warning. I had snow-on-the-mountain once and creeping buttercup too! Wow, now those are invasive!

Marcia! Goutweed! That stuff if almost as bad as the buttercup! You'll never get rid of it! I have some that was planted before we moved here and it still comes back. I have had it for years previously and just accept that it will always be there.

I love lily of the valley and am getting some in a trade this week for my shade garden. I have a little of the pink and it is not spreading either :-(

My mom has Lily of the Valley growing under her lilacs. She has lived in the house since 1970 and we are sure they were there quite awhile before that.
This time of the year the perfume is lovely. The lilacs and the lily of the Valley.
Has it taken over her yard no. Stays right where she wants. yes it is a big patch.
I have been trying to grow it under a maple in my back yard for years.it sure is taking it's time.
I think it counts on attitude whether you are willing to let it have space or not.

Yep, goutweed. Where it is, i won't want to get rid of it and it's a little isolated from the flower beds. It's on a slope in deep shade.

So far none of my lamiums have become invasive, but i don't think i have one with yellow flowers. I love lamium aureum and 'White Nancy' as well, but some of it is lost every year when we get cold weather after the snow is gone. I forgot to look this year to see if there's any left.

marcia - you are in zone 3 which probably helps control goutweed. Over here in zones 5 - 7, they are particularly aggressive.

I like lamium and have so far no trouble with them - however I did take some precautions to prevent spread - like surrounding it with another ground spreader.

Goutweed can be pretty agressive here as well, but probably the cooler climate helps suppress it a bit.