Thanks, I wasn't sure if they could stay under freezing like that and
survive.

If you can turn down the heat to the garage
get one of those cushioned play mats from toys'r us
and place the roses one that. This will ensure the
pots don't freeze from contact w/ the ground.

What a great idea! I wonder if that blue insulation foam would work as
well. The hard part about the garage is that the furnace is there and
even when the space heater part is off, it can be pretty warm just from
the furnace. Maybe I'll try building an insulated rose box in the
coldest corner of the garage this fall--try to protect from both extremes.

The ideal situation is that the tempreture dips
just below 32F every day. As long as the soil
does not freeze your rose will survive.

The blue insulation may work as long as the
pot does not compact it, in which case the
thermal break is lost.

Alternately you could withhold water and keep
the soil just moist. This too helps keep a rose
in dormancy. DO NOT let it go dry.

Would you suggest covering it with something nonpermeable like a plastic
bag (assuming I could get it around the thorns without poking it full of
holes!). Or would this encourage mildew or parasites too much?

I'm not sure what the purpose of this would be.
In any case the roots must also breath so
non permeable may not be a good idea.

I usually put a layer of mulch. This way I only
have to lightly water once a month.


Thank you for such helpful answers and suggestions! My grandfather was
an expert rose man, and I'm sad that I've come to roses too late for him
to have helped me out.

I'm sorry to hear that. He must have been a fascinating person.
Living in the Great Plains it is rare to meet a really knowledgeable
person on roses. Some of the information they acquired through
trial & error was priceless. The loss is lamentable.

Kim


--
Theo in Zone 5
Kansas City