There are measurements for species, such as here:
http://flora.huh.harvard.edu/c...
I can't off the top of my head think of anywhere this is listed for cultivars, unless maybe old ones in Stout's book, I will have a look. But, in theory at least, the measurements may vary between gardens also depending on nutrition, irrigation, climate, positioning in sun versus shade, leaf age etc. Measurements would also have to be of a flattened leaf to remove the folding effect.
Edit: Just skimmed Stout's book and didn't see anything for cultivars. He may have commented on leaf width for species but I'll need to search for that in the digital version later, really must get the stuffing for Christmas dinner made and frozen this morning instead of geting diverted by more interesting endeavours!
