Grapefruit

Shaking Forest trees is the only source, and the odds per tree are poor, so this is something you collect incidentally while chopping wood rather than something you set out to find. Shake everything you walk past and they pile up.

On its own it is a short, weak food buff, worth eating only when you have nothing better. Its real use is as filler in the recipes that accept any fruit at all: Fruit Juice, Fruit Salad, and Ambrosia through Shimmer. There is no grapefruit specific craft, so there is no reason to hoard past what those need.