I would suggest ANY time but from now till blooming. They will probably survive, but will be very stressed.

A bit off the wall suggestion, but it has worked for me.

About 10 years ago I was a lily fanatic and had bought may lilies of many types. I notice with my first Asiatics that as they grew and made baby bulbs, sometimes they traveled a bit and got mixed up with the color planted next to them. As I was a bit of a purist, and didn't really want huge clumps of the same kind, but intended to dig them up after several years to share the babies.

So I planted them in pots before putting them in the ground. Also, if the color combination with the neighboring perennials wasn't what I liked, they were easier to dig up & move.

This worked out quite well until the dreaded red lily beetle hit the garden. I got so disgusted that I dug up most of the pots (one had a trellis blocking access & one had died down so bad that it was hidden under some hosta & daylily leaves) and parked the pots in an uncultivated space away from the main garden. The intent was to compost the pathetic skeletons, but I never got around to it.

Then 3 years ago I was in Machias and saw a garden with Asiatics. I went over & asked the lady if she had any trouble with the beetles & she didn't have a clue of what I was talking about. So I decided to give my daughter-in-law my lilies as she lives there. I did give her a few, but I don't make the trip from Gardiner as much as I would like, and some were too young to be flowering. Some of the tags got lost or unreadable over the years, so I didn't even know what color they would turn out to be.

But having the lilies grouped in a "pot ghetto" made it easier for me to monitor them for the beetles, so they did a lot better than they had scattered in the garden, and I was running out of gardening space anyway.

Last year I decide I rather liked the more mature daylilies that I had made beds for down in the field when I was younger & had more energy. I didn't make the trip down the hillside that often to even look at them close up or pull off the nasty yellowing leaves.

So as they bloomed I went down & dug up the clumps. I was redoing the mostly yellow bed topside that year, so many of them got crammed into there with other perennials, but the orange, red & pink ones joined the bulbous lilies in the ghetto.

This year, I noticed how overgrown the topside beds have gotten, burying some of the shorter plants. So some purple dillies joined the ghetto residents.

I had put some hostas I had dug out of one bed where an unknown vining weed had encroached, after my half-heated attempts in past years to exterminate it from the hillside, which I had potted & put out near the roadside, where I could easily move them before the snow fell.

Then lilies & daylilies got temporarily moved to this feature spot when they bloomed & moved to a less conspicuous spot when they got ratty looking.As soon as it cools down some I plan on potting more of the overcrowded plants and having more of a movable garden.

A long long story about a short suggestion.