Should I get a separate canister for onions, or can I put them in the potato canister?

Onions and potatoes need to be stored far away from each other. One of them releases a chemical that rots the other -- can't remember which :)

I don't believe air tight storage is recommended for either potatoes or onions -- why do you need to store them in canisters.

I don't have much storage so I just don't buy potatoes and onions in quantity.

Well, my cabinets are all crammed. I'm thinking of building a pantry into a foyer closet, but in the meantime, I'm hoping to use counter canisters for food storage. You're right about potato storage, though--a paper bag with holes in it is apparently best.

So I guess I'll just get canisters for sugar and flour.

I don't know what your exact situation is but I have a small galley kitchen with minimal storage. Besides de-cluttering, I store stuff out of the kitchen if it makes sense -- Why wait to convert a closet to a pantry when you can use it for multiple purposes -- get some temporary storage that fits and put some stuff there --

I have a guest bathroom with a lot of drawers which I use for canned goods, baking supplies I use infrequently. I have a very large closet with shelves which I use for a lot of stuff including appliances I don't use often such as my large Cuisinart and my Crockpot. I have flattish baking ware which I use infrequently stored in a plastic chest that slides under my bed.

All of these enabled me to free up space in my kitchen for stuff that I use every day.