Depends upon what type of cuttings you are doing. Stick the cuttings in water - go ahead and experiment now - in the windowsill. Stick them in dirt in a dixie cup and experiment that way too - are you concerned with overwintering in the greenhouse, or what?

Some woody ornamentals cuttings can be held in damp paper towel for a few weeks in the veggie crisper, but you will need to watch for mold. Trouble is the length of a MN winter. If the plant will winter over without loosing all it's above ground stems, then just wait until the weather lets up in very early spring. I can stick dormant woody cuttings in the garden here, and cover with a soda bottle, mulch and it will callus during the winter and root as soon as the soil warms in spring. (Zone 6 will go to zero nearly every winter) You really need advice from someone is your zone. If you will be keeping the greenhouse heated during winter, then you can fall propagate and hold them over inside. Not sure I understand exactly what your reasoning is. Softwood cuttings of woody ornamentals can be stuck in fall and held over winter in a heated greenhouse. I can do it, but it's a big pain when I can just stick them outside and have healthier plants come spring. Don't have to fight disease and insects that way.

For grafting, I take scion wood as late as I can before the buds break and hold it in veggie crisper until the weather warms before using to graft, but that will not be more than about 8 weeks.

Some woody dormant cuttings can be buried in the ground and held over winter for spring sticking...grapes in particular are done that way.

My greenhouse is unheated. I can propagate in late fall, bury the pots to the rim in the greenhouse beds and hold over winter that way. I have hot water pipes under the beds to use when the temps drop below 20*. I'm still talking about woody ornamentals.

Hope this gives you some ideas to work with.

finally getting back to you, i understand must of these? i can see from my looking around, it really depends what type of plant you are dealing with when deciding how to propogate?

about my idea of holding cuttings over winter, i thing i like what you said, why do that when i can just do it in the spring. i think i plan now is get something belt, and then when it warms up in the spring i will go around the yard and start some cuttings. any other tricks you can pass along to a new coming, that would be great. would you please send your info to my email? i sometimes have a hard times finding my info otherwise. thanks, jim.

I think the best bet would be an unheated greenhouse or coldframes for your area. Snow cover, frozen, and soggy soil may hold you back until it's a bit late.

I stick them in early December... they need a few weeks to callus before the weather warms, at which time they should make roots. I found one inch roots on dormant rose cuttings in March this spring. Our estimated last frost date is April 25, but not frost proof until May 10th. Hope that will give you something to compare to.

Old textbooks described burying the cuttings upside down below the frost line. I have been told grape growers once did this for serious. In college I did an experiment with oleander. The upside down cuttings rooted but with oleander so did my controls so I learned nothing from my experiment.

In another experiment with Poplar cuttings taken in midwinter and planted in soil right side up and protected from freeze had more healthy roots sooner than did similar cuttings taken in the spring.

I have had mixed results with buried cuttings. Grapes did fine in zone 7, and concords did well here, but last winter I wanted to start some wild ones and it failed. I also tried with rose cuttings and my percentages were so low with buried cuttings that I never tried that again.

Not sure where Albert lives, but I can agree with the results with Hybrid Poplar...I have stuck them as late as early March and had near 100% take. I have done them fall and spring with no protection and had equally good results. You just have to do the research on each plant that you want to propagate. Propagating may be less problem than getting them through the first winter for you in zone 4.