@Cpschult I have grown LBB for fifteen years and have never seen any cresting on it so I would say that it never expresses. LBB may or may not actually have a mutation for cresting.
Cresting is a genetic effect that suffers from what is called incomplete penetrance and variable expressivity. Some plants that have the appropriate genetics to show the effect will never show it and others will show it sometimes and in different manners. What it basically means is that the visible cresting effect is very strongly determined by the environment and any number of other genes present (and possibly different) in each individual.
LBB may have a mutation for cresting but the rest of its genotype prevents it being shown or it might be the exact opposite in that LBB may not have the mutation but it has the necessary genotype to allow cresting to be expressed more frequently in the seedlings produced when LBB is crossed with a plant that does have the mutation.
