3,473. Where the Rules of Demai Apply
Hilchos Maaser 13:2
The produce that ripens first and last in a valley is exempt from the stringencies of doubtfully tithed produce. Analogous produce grown in a garden is liable because it was guarded. “Produce that ripens first” means that which ripened before its owner hired a guard to protect his crop. “Produce that ripens last” means that which remains after the reapers have folded up their nets and left them unguarded. Similarly, the vinegar of wine dregs is exempt from the stringencies of doubtfully tithed produce.
Hilchos Maaser 13:3
The laws regarding doubtfully tithed produce were only instituted regarding produce from the land that was occupied by the Jews who returned from Babylonia, which is from K’ziv and inward, with K’ziv itself not included. The produce from K’ziv and outward is exempt from the rules of demai because we assume that produce originated in the place where it’s found.