I'd bring them in. They can survive well below freezing once established but bring those babies in for the night.

Roots don't like dramatic temperature swings, so putting in the basement sounds perfect. Don't want to get them all warm either . . .

Why the basement? You’ll be running up and down stairs all the time. They still need as much light as if they were outdoors. I just bring plants I’m hardening off inside the door at night and stick them out again in the morning. They’re perfectly happy on the doormat for a few hours. In fact, unless you know they came from greenhouse, I might even leave them outside against the house wall and put something like an old towel over them at night.

closed garage is probably good enough ...

frost damage is when leaf tissue freezes at the cell level ... there is never any frost in a structure ... maybe a freeze ... but not often ...

welcome to the forums.. its always helpful to add big city location ...

good luck on betting the bank on ma nature and peeps opinion of what she will do .. lol .... i dont know where you are.. but you could probably have a frost or freeze in a month.. no matter what the brainiacs think about it ...

one of the top rules in the garden ... just because you buy it.. get your grubby little hands on them... doesnt mean it proper planting time ...

they are not house plants.. and they dont need to be nestled in for the night ... ever ...

ken

"one of the top rules in the garden ... just because you buy it.. get your grubby little hands on them... doesnt mean it proper planting time ..."

You can take this advice with a large grain of salt :-) If the plant is fully hardy for your zone - and creeping phlox is extremely cold hardy, zone 3 - then you can safely plant as soon as your soil is workable. Meaning not frozen or saturated from rain or snow melt. Just make sure your plant has been properly acclimated to outdoor conditions first. If purchased from a supplier who offers the plants for sale outdoors on a bench or rack, chances are good it has been sufficiently acclimated.

I have been planting and transplanting for the last 6-8 weeks and we have had several frosts over that time frame and with no damage to any newly planted stock.