Requirement is for produce grown from the ground: Shabbat 68a
Requirement is only for Israeli produce: Temurah 21b
Determining a growth's status as "food" based on local or global custom: Eruvin 28a-b
Dirt from outside Israel, on a boat in Israeli waters: Gittin 7b
Produce from Surya: Gittin 8a, 8b
Produce from an un-holed pot: Eruvin 31b; Gittin 7b-8a; Menachot 70a
Produce which grew in an un-holed pot, and then a hole was made and it added growth: Menachot 70a
Whether we gauge by the hole in a pot or the airspace of the branch [and factor in the question of the roots] to determine whether produce is growing in Israel or not: Gittin 22a
Gauging a tree's fruit, where the roots and the branches are in two different areas: Gittin 22a
Produce which was from previous year of the Tithing Cycle still requires tithing: Rosh HaShanah 5b
The produce must grow and be collected while under the circumstances which mandate Tithing: Rosh HaShanah 15a
Tithing is mandated for produce which is of a sort that people will plant: Succah 36a
Types of Produce
Produce which is animal fodder: Shabbat 68a
The Requirement is for food which is to be eaten in a permanent meal: Pesachim 105a; Beitzah 13a
Whether Shabbat renders a meal "permanent," to require tithing of its produce: Pesachim 105a
Using Cleverness to bring in produce with its chaff intact, preventing the obligation: Pesachim 9a; Menachot 67b; Niddah 15b
Using Cleverness to bring in produce via the roof or backyard: Menachot 67b
Obligation to tithe wine which is in the winecellar, which a person drinks while he is actually standing outside the winecellar: Eruvin 20a-b, 99a-b
Produce which had the Maaser tithe separated even before the tithing obligation began: Beitzah 13a-b
For vegetables which were buried beneath leaves: Shabbat 113a
Produce which had Terumah/Tithes separated, and then was replanted, and the original produce remains intact with the growth: Menachot 69b-70a
Above, for onion [which is naturally planted that way]: Menachot 70a
Produce which was brought indoors with its chaff intact: Pesachim 9a; Beitzah 13a
Under-ripe, stunted fruit: Eruvin 28b; Succah 36a
Fruit which is of a sub-species that never reaches the edibility of the rest of the species (like crabapples): Eruvin 28b
Bitter almonds vs. Sweet almonds: Eruvin 28b
Vinegar: Niddah 2b
Fruit which could be treated in order to make it edible: Eruvin 28b
Kitniyot brought inside in their original bundles: Beitzah 13a
Wheat kernels, barley kernels: Beitzah 13b-14a
Onions: Beitzah 13b
Gourds: Beitzah 13b
Ownerless Produce [הפקר hefker]
The tithing requirement is for produce which is guarded, not ownerless: Shabbat 68a; Succah 39b
Considering produce to be under a person's protection, and so not ownerless, if he is guarding the area in which it lies: Pesachim 6b
Produce which was declared ownerless, and then harvested by the former owner: Nedarim 44b; Temurah 6a
Fruit which fell from a tree overhanging or abutting Public Property: Bava Metzia 21b
Viewing produce owned by a kohen as though it had been tithed and the tithe is just there in the mixture [מתנות שלא הורמו כמי שהורמו דמיין]: Bechorot 11a
Produce inherited by a non-kohen from a kohen maternal grandfather, who inherited it from a non-kohen maternal grandfather: Bechorot 11a