There' a historic truth there, from settlers in covered wagons wanting to try to grow roses in their new locations and trying to bring them on a months-long trip. Sticking the cutting in the potato might keep it from desiccating for some time, possibly having taken root by the time the trip has ended. Although it may have sometimes worked, there's nothing about doing this that would cause it to be a preferred method for attempting propagation, unless your cutting does need to spend a few weeks in a covered wagon. What probably happened much more often is that the potato took root. I've only seen this "advice" in regard to roses, but if previous generations were employing this method for some reason for roses, surely other plants got involved too. The confused version of this old tale, that it's worth doing in regard to regular, no-travel-involved-propagation, has gone viral for some reason lately, but should probably remain a discussion about history, and example of the determination and imagination a plant-o-phile can have. :+)
