You definitely want to put them on a cookie sheet in the oven, set about 250F for about 20 minutes. Kill the fungus and mold that's probably on them, any hitchhiking bugs. Rinse them off before baking, just to remove surface dirt (I think it might help keep them from getting too crispy while baking, too). I do this with twigs and small branches, too, and any bark I'm putting in the tank.