Related for Bava Batra 285:10

Vegetables that they are accustomed to watching over for one day [after they are harvested, before they begin to spoil], they they take terumah on their behalf for one day; two days, they take terumah on their behalf for two days; three days, they take terumah on their behalf for three days. The cucumber, the pumpkin, the "kitchen vegetables" (=טרכסמין, esp. endive, see Jastrow), and beets are what they are accustomed to watching over for one day [and] they take terumah on their behalf for one day. The lettuce, and the leek, and the turnip, and the carob are what they are accustomed to watching over for two days, [and] they take terumah on their behalf for two days. The scallions and the sweet melons are what they are accustomed to watching over for three days, [and] they take terumah on their behalf for three days. This is the general rule: Everything is watched over, we [may] take terumah on its behalf. Rabbi Nechemiah says, we do not take terumah from mulberries that are harvested in the morning on behalf of mulberries that are harvested in the evening. And so too Rabbi Yosei would say, there is no bitterness in cucumbers except for its innermost part -- behold, this one supplements the outer layer [of the cucumber with additional non-bitter produce, presumably equivalent to the bitter area inside the cucumber] and thereby takes terumah.