Types of Grain Requiring Hafrashas Challah

Only dough made from the five grains [wheat, barley, spelt, oats, and rye] – regardless of whether it will be used for bread, challah, cake, etc. – requires hafrashas challah (שו"ע יו" ד סי' שכ"ד ס"א ).

Dough made from the minimum shiur of flour that is a mix of the five grains, e.g., a mixture of wheat and spelt, also requires hafrashas challah (שו"ע שם ס"ב ).

If a woman made two batches of dough, each from a different type of flour and neither containing the minimum shiur, and she does not want the two to be mixed, sticking them together does not combine them for the shiur (שו"ע סי' שכ"ו ס"א ). If she does not mind the two getting mixed, see Shulchan Aruch (סי' שכ"ד ס"ב ) for the specifics of which flours can combine with each other.