Just going to add a side note. I probably wouldn't have lumped these back under variety. Silphiums are likely to be split out more rather than lumped back in, in future. I do understand that it follows POWO, and honestly there's not a satisfying Silphium treatment (Mason Brock's treatment in Flora of the Southeastern US is the best I've used and even he admits it's not perfect). For now this is probably the logical step, but I expect this may be undone in a few years.