What environments can farm areas have?

The same four zones turn up under two names each, so don't read them as eight options. Cold also appears as cool, and scorching also appears as scorched. Freeze and warm keep their names.

That gives you two zones on the cold side, freeze and cold, and two on the hot side, warm and scorching. Which seeds belong in which zone, and what each crop turns into, is covered in the Homeland Crops article linked from this page.

Not settled: The list of farm environments is given as "including" these four, so it may not be the full set.