Hey Ken, I wouldnt worry about it. About 15 yrs ago, I planted 4 Lily of the Valley plants. Two on the side of a shed, the other two on the side of our house where nothing but weeds lived.
Although they multiplied, for some reason they didn't grow beyond a wire fence, on our side of the property. And believe me, no generic, wire fence is going to keep a weed from entering neighboring property. Maybe it's obiendient LOTV..lol.
Lily's not the quickest growing plant anyway. If it starts to spread in your yard, just pluck them. If you pluck at a young age, you've got it beat.
I wish it was that simple with weeds, they grow everywhere.
LOTV looks nice in rows. Oh, the best part, when Lily's are planted in groups, weeds pretty much stay away.
Lily of the Valley is somewhat toxic, so if you have pets/kids, keep watch. Toni

Thanks Toni!
My neighbors try to tell me that it will spread out of control, but I have my doubts..
I don't worry about the toxicity of the plant, because I don't have any young kids around and have indoor birds for pets. I'm sure it will be fine.
I did plant them in a nice row, so I bet it will look nice. Another plus is that half of them are pink LOTV. So they are planted white, pink, white, pink, etc. Cool beans! lol
Thanks again,
kentstar

I think it really depends on where you live because I've been trying to rip it out for ten years and have not succeeded.

I've used Round Up, hang digging, mowing all the foliage off to starve them and spread heavy mulch over them to smother them.

They've spread amost twenty feet along the boxwood hedge and out into the lawn....