MudderChuck

I'm not an Apple expert but most new plant starts (cuttings) do best in the seasonal transition, springtime. Growth is accelerated and the cuttings are more vigorous.

I've heard of a trick that works for many plants, put the cutting in the refrigerator for a while (best guess a month), and trick it into springtime growth. A plants clock is part seasonal (calender) and part temperature, so IMO the results can be iffy. They recommend against having too many leaves. But contrary to popular wisdom for many plants I've had better luck having starts with a flower bud or two, seems to encourage vigorous growth, The tops seem to be more vigorous also I usually use around 8-12 inches of the top woody not green, with a bud, and contrary to what I've read, scrapping a little bark off one side of the cutting just before putting it into a medium (I use regular old peat moss type flower pot mix) this seems to promote root growth. About half the cutting in the potting mix. I read the label on the potting mix, you want very little fertilizer. The root system can take half a year to develop. I use the shotgun approach, many of the cuttings may develop disease or just not grow before they die. The survival rate is likely to be 25% or less. Just some general tips and not really Apple-specific.

My next question would be why? Do you have a superior variety? Or are you like I am., just curious and like to experiment? There is likely to be many tips on the internut. Around here Apple starts are easy to come by, inexpensive, and too many varieties to mention. I buy mine from a local Gardening Club.

If you have an exceptional tree I'd try some cuttings and root grafting. I lost an exceptional Apricot winter hardy tree many years ago and really wish I'd started some clones. The fruit was more like Peaches than Apricotes, sweet and delicious.