I can't check my 'Highland Lord's leaf width at this time of year unless I do it with dead foliage but right now it's dark outside. On the bright side, at least the dead foliage should be visible since there's no snow on the ground - yet (it's actually raining this morning).
But, for plants in general, those with narrower leaves are typically more heat, drought, sun tolerant than plants with wider leaves (less transpiration and less surface area to get over-heated by sun).
Becky, perhaps a wider leaf seedling may have more stomata and therefore more entry points for rust. There'd also be more surface area on a wide leaf for spores to land on. In some other plants with similar architecture I seem to recall that upright leaves are less susceptible than more arching ones because it is harder for spores to settle on something vertical as opposed to horizontal. Have you noticed anything like that?
