It seems that scale creep is a very real thing! This is Nolzur's delightfully brutish and verdant Shambling Mound. For a Large creature it is very large indeed, easily the size of a tabletop-scale elephant or bigger, and extending way off a 2x2 base with its outstretched limb.
I put some straight-pin mushrooms on it, as I do.
Here's a group shot with Reaper's beautiful Swamp Shambler and a WotC grab-bag Dryad and Needle Blight, for scale comparison.