Tasty Watermelon Jam

I never thought about making jam from watermelon until I had way too much leftover from a backyard barbecue last summer. It seemed like a waste to throw it out, but we were all so full of burgers and potato salad that nobody wanted another slice.

Turns out, watermelon makes a pretty great jam. It’s sweet, a little tangy with the lemon, and it has this light, summery flavor that’s perfect on toast or biscuits. The trick is using pectin to get it to set properly—watermelon has a ton of water in it, so without pectin, you’d just end up with syrup. I use Ball RealFruit Classic Pectin because it works every time, and I’ve learned that consistent results matter when you’re canning.

What Kind of Watermelon Should I Use?

Any ripe watermelon will work great for this jam, whether you grab a seedless variety or go old-school with a seeded one. If you’re using a seeded watermelon, just make sure to remove the seeds before pureeing – nobody wants to bite into a crunchy seed in their jam. The key is picking a watermelon that’s nice and sweet, so give it a tap and listen for that hollow sound, which usually means it’s ripe and ready to go. You’ll need about 3-4 cups of cubed watermelon to get the 2 cups of puree this recipe calls for, so plan accordingly when you’re at the store.

Options for Substitutions

This simple jam recipe allows for a few tweaks if you need to make substitutions:

• Watermelon: You can use any variety of watermelon for this recipe – seedless, seeded, or even yellow watermelon. Just make sure to strain out any seeds before pureeing if you’re using a seeded variety.
• Lemon juice: Fresh lemon juice is best, but bottled lemon juice works in a pinch. You could also try lime juice for a slightly different citrus note.
• White sugar: While you can reduce the sugar slightly since this uses low-sugar pectin, don’t skip it entirely. Sugar helps with preservation and texture. You could try using 1 ½ cups sugar if you prefer less sweetness, but the jam may be softer.
• Low-sugar pectin: Don’t substitute regular pectin for low-sugar pectin – they require different sugar ratios and won’t set properly if swapped. Stick with the low-sugar or no-sugar-needed varieties like Sure-Jell or Ball brand for best results.

Watch Out for These Mistakes While Cooking

The biggest mistake when making watermelon jam is not using enough pectin, since watermelon has such high water content – stick with the full 6 tablespoons of low-sugar pectin to ensure your jam actually sets instead of staying runny.

Another common error is skipping the lemon juice or reducing it, but that acidity is crucial for both flavor balance and helping the pectin activate properly, so don’t leave it out.

To avoid a watery jam, make sure you’re measuring pureed watermelon and not just chopped pieces, and consider simmering it a bit longer if it still looks too thin after 20 minutes – it should coat the back of a spoon.

Finally, resist the urge to skip the second boil after adding the pectin, as this step is essential for the jam to reach the right consistency and properly preserve.

What to Serve With Watermelon Jam?

This sweet and summery jam is perfect spread on warm buttered toast or English muffins for breakfast. I love using it as a topping for cream cheese on bagels, which gives you a nice balance of tangy and sweet flavors. It also works great swirled into plain yogurt or spooned over vanilla ice cream for a simple dessert. If you’re feeling creative, try using it as a glaze for grilled chicken or pork chops – the fruity sweetness pairs surprisingly well with savory meats.

Storage Instructions

Store: Once your watermelon jam has cooled completely, store it in clean jars with tight-fitting lids in the refrigerator. It’ll stay fresh for about 3 weeks, which gives you plenty of time to enjoy it on toast, biscuits, or even swirled into yogurt.

Freeze: If you made a big batch, watermelon jam freezes really well for up to 6 months. Just leave about half an inch of space at the top of your jars or containers since the jam will expand as it freezes.

Thaw: When you’re ready to use your frozen jam, move it to the fridge and let it thaw overnight. Give it a good stir before using since it might separate a little bit during freezing, but the flavor will still be just as good.

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 900-1000
• Protein: 1-2 g
• Fat: 0-1 g
• Carbohydrates: 225-250 g

Ingredients

• 2 cups watermelon (finely diced into 1/4-inch pieces with seeds removed)
• 2.5 oz lemon juice (I prefer ReaLemon for consistent acidity levels)
• 1 3/4 cups sugar
• 6 tbsp pectin (I use Ball RealFruit Classic Pectin for the best set)
• 1/4 teaspoon salt
• 1/2 teaspoon fresh lemon zest

Step 1: Prepare the Watermelon and Measure Ingredients

• 2 cups watermelon
• 2.5 oz lemon juice
• 1 3/4 cups sugar
• 6 tbsp pectin
• 1/4 teaspoon salt
• 1/2 teaspoon fresh lemon zest

Dice the watermelon into 1/4-inch pieces, making sure to remove all seeds as you go—this prevents any unwanted texture in your finished jam.

Measure out all remaining ingredients and have them ready near your cooking station.

This mise en place approach means you won’t be scrambling to find ingredients once the mixture starts heating and thickening.

Step 2: Combine Watermelon, Sugar, and Lemon Juice

• 2 cups watermelon
• 1 3/4 cups sugar
• 2.5 oz lemon juice

In a large heavy-bottomed pot (at least 4-5 quart capacity), combine the diced watermelon, sugar, and lemon juice.

Stir well to combine, then bring the mixture to a rolling boil over medium-high heat, stirring occasionally to prevent sticking.

This initial boiling helps the watermelon release its juices and allows the sugar to dissolve evenly, creating a more cohesive jam.

Step 3: Add Pectin and Reach Full Boil

• boiling watermelon mixture from Step 2
• 6 tbsp pectin
• 1/4 teaspoon salt
• 1/2 teaspoon fresh lemon zest

Once the mixture reaches a rolling boil, reduce the heat slightly to medium and sprinkle the pectin over the surface while stirring constantly for about 1-2 minutes until it’s completely dissolved and no lumps remain.

I find that stirring continuously prevents the pectin from clumping and ensures even distribution throughout the jam.

Once the pectin is fully incorporated, return the mixture to a full rolling boil and stir in the salt and lemon zest.

Step 4: Simmer and Cook Until Set

• jam mixture from Step 3

Maintain a full, rolling boil for exactly 1 minute, stirring constantly—this brief intense heat activates the pectin’s gelling properties.

Then reduce the heat to medium-low and simmer gently for 20 minutes, stirring frequently to prevent the bottom from scorching and to encourage even cooking.

The jam should darken slightly and become more viscous during this time.

To test if it’s ready, place a small spoonful on a cold plate; it should wrinkle slightly when you push it with your finger, indicating proper set.

Step 5: Jar and Cool the Jam

• cooked jam from Step 4

Remove the pot from heat and let the jam rest for 2-3 minutes to allow any foam to settle.

Carefully pour the hot jam into clean, sterilized jars, leaving about 1/4 inch of headspace.

Wipe the rims clean, seal with lids, and let the jars cool completely at room temperature for at least 6-8 hours before moving them.

The jam will continue to set as it cools, reaching its final texture by the next day.