3,472. Produce That Can Be Assumed to Be Ownerless

Hilchos Maaser 12:18

Let’s say that one person sells food to another and, after delivering it, he tells the buyer that the produce is untithed, or the meat is from a firstborn (which is sanctified), or that the wine was poured as a libation to an idol. Strictly speaking, he is not believed (since the item is no longer his), even if he’s a learned person, though someone diligent should act stringently in such a situation. If one believes the seller, he is praised for it, even if the seller is an unlearned person.

Hilchos Maaser 13:1

If produce can be assumed to be ownerless – like wild figs, berries, apples and other wild fruits, anise, dates that fell off the tree before swelling, capers, coriander, and more – are exempt from acting stringently when doubtfully tithed. One who buys such things from an unlearned person need not take terumas maaser or second tithe from them because we assume that they grew ownerless. Even if an unlearned person says that they were untithed, they are exempt from tithes until it is established that they grew from guarded produce.