I am curious; why are they in pots? Why haven't they been planted in the ground?
The perennials you listed can be planted in the ground and survive zone 5 winters without any problem, unless they are transplanted too late in the fall and have no time to settle down.

If you need to keep them in pots, then burying the pots will give them a better chance of survival from the freezing and thawing in the winter.

In pots because i thought i would have 1 more plant sale before the fall.
I guess i will transplant into garden beginning of sept.

Buddleias are iffy in zone 5 and even more so with fall planting. If these are small plants, I would mulch them very heavily. Montauk daisies may never have time to flower in zone 5; they bloom quite late. Salvias (if they;re not tender species) and Coreopsis should be fine.

Hi ski .... - I've been butterfly gardening since the '80s ... simply called 'mixed perennials' I have all mentioned & several others in different beds ... many will survive our zone without thick overcoats. Last Winter was a record Killer, in recent years here - nearly killed my beloved B' Bush ... showed up later than late habit & doing great entertaining lots of Monarchs, Swallowtails & many smaller ones.

Perhaps for your holding beds, you might try, opened, huge, cardboard boxes, held down with bricks, over collected dry leaves & topped with more leaves ... should be more than ample, since they are young & newly planted perennials this Fall.

I've used this method on my tender bloomers ... works well!

Good luck & hope you have a good Fall sale!!! Â;)

Would NOT recommend leaving them in pots, even if you bury the pots. Once the soil in the pots freezes, the rims will hold water and it won't drain... Winter wet can be a real killer...

Beth