Does anyone have a suggestion for a good way to store wooden or plastic calls during the offseason in a very dry climate like Denver, CO? Last year I stored mine in a ziplock bag with a wet sponge, but that seemed to be too much moisture as there was mold on the wooden calls in the fall.

kind of hard to practice with your calls all wrapped and stored

Never store calls as you did. They should be stored with your guns in a clean dry place and as was already said, how can you practice if they are stored till next season. If I were you I would throw the wet moldy calls away and get some new ones.

yah like some duck commanders