Although freezing watermelon is unconventional, it is an effective way to prevent a prolific garden harvest or a too-large melon from going to waste. You can freeze watermelon and delight family and friends with a bowl of sweet, colorful melon during the dark days of winter. Serve the melon or incorporate it into desserts or smoothies while its still frosty, because the fruit tends to get mushy when completely thawed. Frozen watermelon retains its quality for at least eight to 12 months.
It's Just Ripe
Firm, ripe watermelon is more flavorful and holds its shape when frozen better than unripe or soft, overripe melon. Freezing a substandard or unripe melon doesn't improve the quality of the fruit. Scrub the melon, then slice it in half and remove as many seeds as possible. You can remove the rind and cut the melon into chunks, slices or cubes about 3/4 to 1 inch in diameter, or you can use a melon baller to create uniform, rounded shapes.
Glass or Plastic
Plastic freezer containers are commonly used for freezing fruit because they are inexpensive, sturdy, stackable and unbreakable. You also have the option of using glass canning jars, which are tempered to withstand temperature extremes. Large-mouth jars are best because narrow-mouth jars are more prone to break at the neck. Avoid mayonnaise or spaghetti sauce jars, which may break in the freezing temperatures.
Tart and Tangy
Freezing unsweetened watermelon requires simply packing the melon into clean, airtight containers with about 1/2 inch of headspace to allow for expansion. If you want melon balls that retain their shape, you can place them on a single layer on a foil-lined baking sheet. Place the baking sheet in the freezer until the melon is frozen solid, then transfer the melon balls to freezer containers or resealable plastic bags.
Sweeten Up
Freezing sweetened watermelon works well for frozen desserts or slushies. Make a light to medium syrup consisting of 1 to 2 cups of sugar for each 4 cups of water. Stir the sugar in warm water until the sugar is completely dissolved and the water is clear, then chill the syrup in the refrigerator. Pack the melon into containers, then pour the syrup over the top, using enough syrup to cover the fruit.