had i discussion but that topic in my thread:
http://discourse.stonehearth.net/t/savegame-coop-passive-multiplayer/20267/15
basicly a culture adapts and is influneced by their habitat and biome. so rayya should never have non-desert crops and recipies for these, with the same issue with the ascendants, why should they have any seeds and recipes for all types of food? so cutting of the access makes sense, but needs a bit balance gameplay technically, like shapeless recipes: flour and later bread can be crafted with corn and wheat since the basic technic is the same. So corn and wheat could havethe the same role in the cultures, they could have bonus yields according to a fitting placement/biome, but there’s no need to disable 'em completely (= players could trade if they want all kind of crops and you can still play a culture in a unfitting biome)
additionaly you can make differences with flexible crops and biome specific ones: rice in a desert = nope, cactee in swamp =nope, so these two would be biome specific and obviously culture specific, corn and wheat would be flexible accoridng to the biome, so they could be used as culture specific ones and having the same role in the food plan.
and level depending crops is a bit boring and makes no sense, why not seperate them in, basic culture crops (absolute basic and needed food stuff), advanced crops (some special food items and raw resources like silkweed), green thumb (farmer can now plant and yield all kind of crops). to create diversity you can have alternatives for some crops, which look different but are technically the same like corn and wheat, and limit the access by trading and exploring requierement. So you have at start 2 food seeds and 1 resource seed and all other seeds need to be found in the enviroment or traded with merchants or other players (something like in banished)