Does anyone have any direct experience of taking cutting from apples? I am aware that apples are usually grafted, however, I want to make comparisons between cultivars on their own roots and those on named rootstocks. My first thought is hardwood cuttings, but I would like to know if there is a "recipe" that works before just applying general principles.
I'm dubious of the premise, but sure, give it a try.
When looking into some of the more extreme propagation methods for another question, https://gardening.stackexchange.com/a/29992/6806 I found a description of a setup where bottom heat was employed to encourage rooting while the tops were kept cold to prevent them from deciding to leaf out before there were roots to support them. It was also described as complex and/or costly to do such that it was not a common technique. I'm fairly sure hormones were also employed.
Here is that link, which still seems to work as of today: "A. D. Webster (1995) Temperate fruit tree rootstock propagation, New Zealand Journal of Crop and Horticultural Science, 23:4, 355-372, DOI: 10.1080/01140671.1995.9513912"
While it is aimed at propagating rootstock, it should be fundamentally applicable to propagating apple cultivars, as both are apple trees of a sort.
From what I understand, "micropropagation" or tissue culture may be a somewhat more reliable (if also somewhat more involved, and equipment/chemistry intensive) approach, but I have not tried it. I have done "casual" hardwood cutting propagation with more failures than successes, suggesting that a less-casual approach is likely required for a reasonable success rate. What it's actually done for me is to make the "traditional" approaches look pretty sensible, on balance.