Regarding 'Jim Dandy': If it is a potato-leaf variety, even if unstable for many other traits, it shouldn't be able to throw regular-leaved progeny without them being the result of a new cross... (ignoring the lower incidence of reversion mutations) since the potato-leaf trait is the recessive form.
So, a site claiming that their potato leaf variety may occasionally throw regular leaf offspring not only suggests instability, it also suggests they don't have good controls to prevent hybridization in their seed source.
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