Casting a goodberry spell upon a handful of freshly picked berries makes 2d4 of them magical. The caster (as well as any other caster of the same faith and 3rd or higher level) can immediately discern which berries are affected. A detect magic spell discovers this also. Berries with the magic either enable a hungry creature of approximately man size to eat one and be as well-nourished as if a full normal meal were eaten, or else cure 1 point of physical damage from wounds or other similar causes, subject to a maximum of 8 points of such curing in any 24-hour period.
The reverse of the spell, badberry, causes 2d4 rotten berries to appear wholesome, but each actually delivers 1 point of poison damage (no saving throw) if ingested.
The material component of the spell is the caster's holy symbol passed over the freshly picked, edible berries to be enspelled (blueberries, blackberries, raspberries, currants, gooseberries, etc.).