My Invincible is only two years old. I consider it as a small.

Here is a link that might be useful: How to post photos

I've had Invincible over 10 years and can see where it get's its name. Mine is not bothered by pests, increases at a "just right"(medium) rate and provides a nice contrast (dark solid green) to surrounding variegated hosta. It can take quite a bit of sun. To answer original---I'd say it's a medium/large.

Mine is a medium,I would say. Phil

Welcome to the forum weekendweeder! I think you're 'gonna like it here'. No question is too silly to generate silly answers (and lots of really good info too). You'll laugh a lot and learn a lot and buy a lot of hostas.
Jan

My invincible is 3 years old. It's in a pot, which retards it's growth somewhat. Mine's 20" wide and about 8" tall. I expect it will get bigger.

bkay

Hi weekendweeder. I have a mature Invincible and it is easily 20-24 inches tall and about 4 feet across. Here is an old pic. Phil

Wow, yours is perfect. Mine's a scraggly looking thing right now. I put it in the ground shortly after reading franknjim's post, so if it actually gets medium/large in a few years, I'll just move or divide.

Oh my, that is an impressive Invincible! I did not expect it to look anything like that, mine is new this year too, and dark dark green, but not showing me much yet.

The comments I've seen about it include that it is not really "invincible" to slugs, so be careful about that and watch. But so far, no slugs on this one of mine.

The comments I've seen about it include that it is not really "invincible" to slugs, so be careful about that and watch.

I'll second that sentiment, mine I'm afraid has proven to be a bit of a slug magnet, in spite of the substance of the leaves. My oldest division is just nicely coming into its own this year and is looking very special, cannot wait for it to start blooming....BUT, being potted it unfortunately is not quite as magnificient as Phil's...

Pieter