As Ken is suggesting, often the answer is more about culture than the genetics. Who knows, for example, which will get larger in full sun, given the tendency for the Sum and Substance family to thrive in full sun (with enough water) while other hostas often stay smaller, and have smaller leaves, in brighter light? Since many hostas will increase year after year, virtually a continuously expanding colony, there is really theoretically no limit. If we are talking diameter, my "largest" hosta is actually a smallish one, some kikutii, that has colonized a large area and that is all "one plant" because it is all connected underground by the rhizomes. You also have to define what you mean by large - height or width. Empress Wu is being marketed as the largest because it is so tall, but Komodo Dragon is actually listed as having a significantly larger diameter. I've been through this so many times... don't get lost in the hype. There will always be another "biggest hosta." For years, Sum and Substance was billed that way - long after we knew that green-centered S&S sports grew faster and bigger. In the old days we had fortuneis that were large and designated things like 'Fortunei Gigantea.' And there was Big John, Big Daddy, etc etc etc. T-Rex got a lot of attention... then faded in favor of Komodo Dragon for a couple of years... now Empress Wu... Of course, as a collector, I have them all and I'll be able to answer this question better in a decade - but by then, I guarantee, there will be at least five more major "giant" marketing hostas... Decide where you want a giant, then plant one that doesn't cost too much. If you want green, buy one of the green ones. If you want yellow, buy one of the yellow ones. Frankly, I'd concentrate more on the form of the clump and the quality of the leaves. I am guessing that in about five years, I'll be picking a large green Niagara Falls over a giant (but relatively "plain") Empress Wu.

Beautiful all and exciting for peeps to look forward to. Unfortunately I'm done. No more room except if I need to replace one.

Here's the Empress coming in at 6 ft. (182cm) across and 3 ft. (91cm) high going into its 8th year. It comes back bigger every year, so I'm not sure if it's done growing. Mine is in a lot of shade only getting dappled afternoon sun. I used a plastic/resin Adirondack chair for scale. (I think they're pretty common everywhere?) Behind the chair it starts sloping down a bit, so the Empress is a bit lower. .......Funny thing is that I planted EW there in hopes it would hide the unsightly concrete base for the deck, but I didn't count on The Empress having such long legs! Leaf with Sharpie pen

The soil is just on the top, compost is under. It is a rain barrel cut in half after breaking. So drainage is good. Look at last pic, those round corrugated leaves is what I bought as WU. Heck knows what happened. I do not remember it much in the pot, was busy, then I got tired of waiting it to grow big so I dumped it behind the fence. Maybe it was bad batch?