I've read they spread well in cooler climates. I'm in zone 7, and the 10 or so I planted in 1997 in deep shade haven't multiplied. So if you're in a warmer climate regardless of tree roots, I don't think they'll spread.

Whoops. Forgot to put my zone. I know that my neighbor's LOTV multiply profusely (this is where I am getting the plants from--- I'm dividing her overgrown bed). I just wasn't sure if the deep shade would effect their multiplication. Well, I'm going to have a few branches pruned out of the jap. maple to give it a little room to breath, so they should be fine. Thanx for your response.

Jenny

I have a patch of lily-of-the-valley along the north side of my house in absolute deep shade. They were there when we moved in and the patch must be about 20 years old. I've heard these can spread enough to be a problem, but mine haven't crossed the path yet out of the bed. They grow well here in zone 5. I've over-planted hostas and other shade plants in their bed and they just keep coming. Super tough rascals that I think would be fine with roots of a tree too. Try it! They are so pretty and make me think of 1950's style weddings as they were all the rage back then...a nostalgia flower I wouldn't be without! Molly

I have some lily-of-the-valley plants that I received from my neighbors mother in-laws about 5 years ago. I have some planted under a Norway Maple and they have at least doubled. The area is lightly mulched with wood chips. I hardly ever water under the tree either. A friend of mine took some too, and they are spreading even faster at her house, but not under a tree but on the North to North east side of her house. Give it a shot, you probably won't loose the plants, just may not spread fast.