First tier is the Foraging skill, which allows the harvesting of herbs and wild vegetables. Second tier is Herbology, which allows the harvesting of herb seeds. Research cost includes herbs. Third tier is Agriculture (X). Research cost includes wild vegetables of type (X). Once Agriculture (X) is unlocked at a University, anyone may travel there and receive one seed of (X). An advantage to this proposal is that it allows the addition of new vegetables by merely introducing the Wild (X) variant into the random generator.
As a test, it would be possible to introduce in T2 as "Alternate Agriculture Research" using a new vegetable currently appropriate would be Wild Pumpkin, given the upcoming Thanksgiving holiday.