I would order now, if you're going to do it. I know Schreiner's Irises nulls their warantee if you order past September 9 for zone 5.

With prices halved, try to order "Double" double fans and they will have a better chance of surviving and bloom better for you next year. You might contact the person from whom you want to order, and ask if they are sending double fans or larger divisions.

I'm in Canada, Z5a. Our frost date is the same as yours. I just planted some new ones a week ago and those will be the last I plant this year because we sometimes have a early frost. I like to give mine at least a month to settle in here.

My rule of thumb, passed on to me by more experienced daylily growers in my zone, is to give the daylilies six weeks' growing time before frost.

There are a couple of things you can do to give the plants a better shot at overwintering, too. Mulch very well after the ground freezes. Some people dump as much as 2 to 3 inches of chopped leaves over their beds, including over the daylily crowns. Of course, you want to get that mulch away from the plants in the spring.

Also, you can place bricks or stones around each newly planted daylily, to prevent frost heave. Perhaps you have reliable snow cover in winters, but we do not, and freeze-thaw cycles here are major culprits in killing daylilies. Obviously, you'd place the bricks first, and then the mulch. :)

If you have a sheltered area, you might have some leeway. I have two beds, shaped like half moons and with one of their edges against the house's stone wall and the rest surrounded by a stone patio. The winter before last, which wasn't too cold, I overwintered some calla lily bulbs that I'd forgotten to dig up! If you have a microclimate that is, say, a half zone warmer, you might want to plant any especially valued daylilies in it.

Also, I can tell you from sad, sad experience that if you have any especially wet areas, you do not want to place newly acquired and/or small plants in those. I had late summer and fall-planted daylilies essentially drown in one end of what is otherwise a perfect bed for daylilies. But I hadn't known that there is underground water and/or a very high water table at that end, and all but one plant essentially drowned last winter.

So, make sure your beds have excellent drainage.

Anyway, you wanted to know merely how late to plant. :) I try to shoot for six weeks of good growing. You could always contact the auction sellers and ask whether they'd be willing to ship in the spring.

Here in zone 4 I like to plant before labor day, a couple of times it has been later and the daylilies survived. I do mulch with leaves each fall I don't wait for the ground to freeze have been doing this for many (over 20) years. The leaves are picked up using a leave catcher on our lawn tractor so they are chopped up. One more thing is I don't bother to pull the leaves away from the crowns of the plants in spring. The daylilies grow right thru the mulch and never miss a beat. This is what works for me in my zone 4 MN garden. I remember one of the well known hybridizers saying that he let the leaves in place and his daylilies would grow thru them with a leaf hat. That is when I decided to leave the leaf mulch in place. The mulch completely disintergrates over summer after being put on up to about six inches deep in the fall as the trees drop their leaves. We put them directly on the garden as we pick them up. Why make more work by keeping them for later it is far easier to just empty the leaf catcher bags on the garden as they fill up. I love my garden but try to keep enjoyment in it without making myself a lot of extra work that is not needed here in my climate.

Thanks everyone for the responses. I think its best to wait for spring, no way I get six weeks before first frost if I ordered now. I wish the sales had started earlier, I planted 27 daylillies from Earlybird last year in early august, in mid 90 temps and every one of them bloomed and looked great this year.

Thanks again,
Gale

If you have to plant them late, try taking an empty gallon milk jug and making a little green house over the plant. I did this when I received an order very late one year, and realized I was in trouble. I didn't want to lose them. (In my zone, that was very late November) and they did very well. Do remove the cap so you have a little ventilation each morning, replace it in the evening.
kay

Gale, her daylilies are true "field grown", so they are very tough!

I love the suggestions on this topic because we all find ourselves moving something or planting something a bit late. I've used the "bricks on top" method with good success. And I've used milk jugs for all manner of things in the garden, including mini-greenhouse, spraying weeds next to plants, extra seedling pots, etc. A truly indespensible and inexpensive garden tool!

More great advice, thank you. I like the milk jug idea, I can see were it would be very handy at times.

Thanks,
Gale