I grow Guacamole here in Alabama, and after three years the leaves on it are not all that large. I Don't have 'Impress Wu', but I do grow' Winter Snow' and 'Sum and Substance' and after two years they have much larger leaves than Guacamole. I would think that 'Empress Wu' would be even larger than 'Winter Snow' or 'Sum and Substance' by quite a bit.
I do have a large island bed and it would have room for a huge hosta like Empress Wu'.
Does anyone grow it this far south?