You've done the right thing, but be patient, as tree cuttings can take months to root well. When you see new foliage emerging (apart from any buds that were just about to open right now and so don't count) then it's taken, and you can transplant, though I'd leave it in the container til there's a good bunch rather than just a couple of roots. How it works is that the hormone stimulates auxins already present in the cutting, and they do what comes naturally - form roots and push foliage.

lucy: Is this the general rule about rooting trees?

I have a beautiful tupelo (Nyssa sylvatica) at my old cottage. It's huge and when the leaves turn in the fall, they light up the sky for months. There are a few sprigs growing from the roots. I'd love to get some cuttings.

I have very limited experience propagating plants from cuttings.

How long do you recommend that tree cuttings be? Should they be covered with plastic wrap to increase humidity? Do they need sunlight or shade? Anything else to keep in mind?

Many thanks!
Pam

You'll have more success if you root it in a pot or bed that is misted and shaded by lath. Preferably in a neutral medium or sand. Nutrients are usually in the mist-water.

pinetree: Thanks. I think I can do these things. I need to investigate how to create a simple misting system.

I don't mean to rain on your parade, but you'll not likely have much success rooting cuttings of oak. It has been done, but not with high % success. Working with 'sucker' material will increase your likelihood, since it's 'juvenile' material, but I still wouldn't get my hopes up much.
In general, with most hardwood cuttings, shade - or at least filtered sunlight, with protection against brutal afternoon sun - is helpful, and creation of a humidity chamber(can be as simple as a clear glass jar inverted over the cutting) can be helpful.