North American Fruit Explorers mailing list at ibiblio

[Alan Haigh <alandhaigh@gmail.com>]

Trees that don't root from cuttings still sometimes root above grafts to
rootstock when planted too deep, however the experiment with kakis planted
at a slant, leaving a stretch of the scion in contact with soil is evidence
that kakis might not. though certainly not proof.  The slow strangulation
by way of copper wire might induce above rooting where other methods fail.
You'd just have to try it with a few trees to know.

Lee, do you know of species this trick has been attempted successfully with?