"Root gnome" is awesome.
Why "fungus"? When I think of alchemists, I think of turning lead into gold, as well as flames to heat water solutions of solvents, "spiritualizing" gases, and so on. It is mainly elemental. There is also alot of medical applications, for healing and longevity, but even these seem to use alchemical ingredients. I guess, some of the chemicals come from plants, like scraping dry wine barrels for certain crystals.
I wanted to find something beside 'Earth Gnome', seams that seemed too wide compared to the others... And stuff like 'Brimstone Gnome' felt too precise... but I guess Fungus Gnome could just be something else (maybe related to Fairy Rings? Like, they can teleport or travel between the Feywild and Material World easily? Clay Gnomes could also be a thing, come to think of it.
Let me look up some alchemical substances...
Ooh! How about Salt Gnome or Oil Gnome?