Peah 6:11

If a person harvests and binds his sheaves at night and neglects some because of the darkness, the laws of shich’cha apply. The same is true in the case of a blind person. If a person intends only to reap the large stalks and to return later for the small ones, they are not shich’cha. If a person harvests on the condition that whatever he forgets still belongs to him, his condition is invalid and what he forgets is shich’cha.

Peah 7:1

If an olive tree is known by a particular name - like the Netofah tree once upon a time – then forgotten olives are not shich’cha (because they will inevitably be remembered). The same is true if the tree is renowned for its name – like the trees Shifchoni and Beishani – for its produce, or because of its location, such as if it is next to a landmark. For other olives trees, two overlooked olive trees are shich’cha and three are not. Rabbi Yosi says that shich’cha doesn’t apply at all to olives.