Your subject line is great. I don't think of lilies as "menacing monsters", but a 6' Longiflorum (??!!) They must be beautiful, but I can see how it would be a bit unexpected.

While I've never heard of a longiflorum getting that tall (usually they max out at ~3'), Wikipedia mentions a variety used in the cut flower industry that gets taller, so maybe that's what you got. Were these potted lilies for Easter that you put out (the growers use growth inhibitors), or where these intended for the garden trade?

The safest thing would be to leave them alone until their foliage dies back in the Fall and then move them. But, if they are as vigorous as you say, you can probably carefully move them after they bloom. Try not to break off the stalk or damage too many roots because they need time for the leaves to photosynthesize to build the bulb back up after the rigors of blooming.

Dig a relatively large hole around each one and then feel around with your hands to find the bulbs. I did that last year with my Muscadet (I'm too impatient to wait) and they all came up this year stronger than before. So it can be done, it's just a little riskier and you have to be more careful.

-Helen

Helen, thanks for the advice. I think I'll take a chance on moving those that are most in the way and then hedge my bets by leaving the rest of them until fall.

All of them are descended from a single potted lily delivered by a florist several Easters ago. I divided the batch of baby bulbs produced by the original plant and grew them as patio plants for a few years before deciding to plant them out, by which time all of the pots were full of bulbs. They've always done well but gave no hint of their full potential until this year. Maybe it's the alfalfa tea.

for those that you move, you may want to clip off their flowers/buds first. Moving could be tramatic and assuming root damage will occur, you wouldn't have buds/flowers draining the plant's energy reserves in case they need to divert energy to developing new roots.