In the Aggaññasutta (DN 27) there is a series of vegetations that evolve as foodstuff for beings. It’s not always obvious what exactly they are.
After the disappearance of the first food, “earth nectar”, there appears bhūmipappaṭaka. Bhūmi is “earth, ground”, while pappaṭaka is said in Pali dictionaries to be a water plant or a mushroom.
The Sanskrit parallels here have parpaṭaka, which is the same in both the Hybrid Sanskrit Mahavastu and the Mulasarvativada Vinaya in classical Sanskrit. The dominant sense is a “thin cake” (“papadam”), but as so often with Sanskrit there are several other senses too.
The reading here is unclear, as some Pali manuscripts have pappāṭika. There is another Sanskrit word prapāṭikā in the sense of a young sprout or tendril, while the Pali papaṭikā (or pappaṭikā) is said to mean either “bark” or “sprout”.
The unifying sense of “thin cake” and “bark” would be “crust”, and perhaps that is the sense here, a layer or crust formed on the earth.
But there is another reference at pli-tv-bu-vb-pj1:2.2.5, where Moggallāna suggests that, to alleviate famine, the monks might eat the pappaṭakojaṁ (“pappaṭaka-nutrition”) under the earth. It seems hard to reconcile this with the sense “crust”, and more likely it is a kind of tendril that lives underground.
In DN 27, they are compared to mushrooms. I think these are the fungal mycelia of a mycorrhizal network. Such fungi spread like tendrils underground, sometimes appearing above the surface, and facilitate sharing of nutrients and information between organisms.
I will probably translate it, then, as “ground-fungus”. @Brahmali you currently have “sprouts”, what do you think?