Hardy Lilies don't spread fast, so I don't think they'd cause problems even if they weren't planted in containers. RAH has some planted in his ponds, ask him or Bill Cody how fast they spread. Bill has some in his ponds too.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).