As a general rule, freezing fresh potatoes is not recommended, according to the Penn State College of Agricultural Sciences. The water in a potato separates from the starch during freezing, so the potato has a watery texture once thawed.
If potatoes must be frozen, small, waxy varieties, such as red or gold potatoes, freeze better than russets. Potatoes should be completely cooked and cooled before frozen. Cooking stops enzyme reactions that lead to discoloration.
To freeze mashed potatoes, cook the potatoes normally, cool and form into 1/2-inch patties. Flash freeze on a cookie sheet, then move the patties to a freezer bag. Since cooked potatoes lose flavor quickly after frozen, consume them within a few weeks of freezing.