There are many challenges in medieval gardening, and reliance upon translations is surely one of them. For example:
Here are two translations of the same line from Le Menagier de Paris.
"nota that runners take root well in the same year they are planted, if they are planted with some roots"
"Note that rooted cuttings bear shoots the same year they are planted"
So if the second version is true, we have direct evidence for rooting cuttings as a method of propagation, whereas the first quote would only apply to plants that send out runners. This is not unreasonable as some plants lend themselves particularly well to this sort of thing. This is Tania Bayard's translation from her _a medieval home companion_
Greco&Rose is the first, from _the good wife's guide_ and they have an interesting footnote about this passage. The presence of the footnote indicates that they are insufficiency satisfied with their translation, but it provides additional commentary and the potential for another method of propagation
"this probably refers to offshoots of plants (suckers) that may be fastened down into the earth...they then form roots and later may be cut free, dug up, and planted elsewhere. Middle French has 'marquetz', "layers". Layer is the botanical term for a stem covered in soil for rooting; 'layering' is propagating plants in this manner."
So clearly the two translators each have a different form of propagation in mind from this original passage. So the medieval gardener has a couple of choices here. First he can learn middle French and tackle the original. Second, she could learn about each of the translators, their style and focus and awareness of horticulture in order to make an educated choice between the two translations. Third, he could just pick one by preference, personal agenda, or at random. Fourth, she could compare other contemporaneous writings to see if either propagation method is supported by other writers.
Thus without further supporting evidence, we are in a sort of gardening limbo, with a source that potentially supports two different, though both vegetative, methods of plant propagation in period.