I got a large container and filled it with 5" of dirt. They buried themselves and emerged in May and June.

I've attached a simular picture of the container I have. I got mine at Target cheap. Mine is semi clear with a gray lid.

I would think you could use a cardboard box as well.

Good luck!

Here is a link that might be useful: {{gwi:542832}}

If the soil in your pot is loose, let the hornworm pupate in the pot. Don't move it in. Just leave it until next spring. It shouldn't eclose this late in the year. This will most parallel what happens in nature.

So the fact that the soil in the pot will definitely freeze solid is not an issue? (Keeping in mind it is on an unprotected balconey........)

If I were to bring the pot in, temps will likely be too warm resulting in premature emergence, I would think.

Could you put the pot in a cardboard box or a plastic box that would provide some protection? You could also line the box with newspapers. You just want to allow the pupae to have the same temperatures as the soil about 5 inches below the surface. And, in your neck of the woods, that may be above the freeze line. If so, then I wouldn't worry about the pupae.

I'd be tempted to take the worm and put it in a gallon-sized plastic bag filled with torn strips of paper toweling. Then I'd watch for pupation. Afterwards, I'd put everything in the produce drawer of the refrigerator until the weather begins to warm up in the spring.

I put 6 Tomato hornworms in a plastic container full of paper towel strips last fall to over winter. I kept them on my patio in a sheltered place. When spring arrived, I removed the paper toweling and left the pupae bare until they eclosed. Every one of them eclosed just fine. But, our winters are a lot warmer than yours.

My concern is - it will most likely wonder from the pot. Mine go clear across the yard although they have ample room and fluffy soil where the tomato plants are kept in raised beds.

I over wintered them in the garage. Do you have a storage room?

Nope no storage room. Turns out it is now a moot point. Right after I last posted, I went out to peek at the fat bugger and he was gone. Didn't see any sign of soil disturbance so perhaps he did wander away. Hopefully he didn't get eaten.