Homemade Strawberry Rhubarb Jam is a delicious spread for toast, yogurt, or dessert recipes. Thanks to the low-sugar recipe, this jam tastes fresh and bright, just like real fruit.
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That magical few weeks when strawberries and rhubarb are ripe at the same time just beg for baking and jam making. Once you’ve already made at least one gluten-free strawberry rhubarb crisp, it’s time to make jam!
STRAWBERRY Rhubarb JAM EQUIPMENT
- Jars! Canning jars only (don’t use leftover mayo, jam, or pasta sauce jars from the store). I recommend 8 oz jam jars, or pints if your family goes through jam quickly.
- Clean, never before used canning lids
- Canning rings
- Pomona’s Pectin (or another low-sugar pectin brand)
- Water bath canner or deep stockpot with a jar rack.
- Large saucepan. I adore my dutch oven for so many reasons, and jam season is another one of those reasons! Having a wide pot with high sides is best for making jam as it allows the jam to process at a rolling boil without slopping over the sides.
- Ladle
- Funnel
- Jar lifter
- Clean washcloths and towels
- Medium mixing bowl
- Something to stir with (I love this thingy)
- Knife and cutting board
- Comfy shoes
Check out this Canning Supplies and Equipment List for a detailed explanation of all the supplies and brands I recommend, as well as ideas on where to find items for free/cheap.
HOW TO MAKE STRAWBERRY Rhubarb JAM
*A detailed and printable recipe is available at the bottom of this post
CANNING PREP
Prepare your water bath canner by filling it halfway with water, and setting it on the stove. Turn the burner to high. Once it reaches a boil, reduce it to simmer. You want to keep the water hot so that everything is ready when the jam is.
Wash and clean your jars. You’ll want to keep them warm to avoid having them crack when placed in the canner. You can fill them with hot water, or place them on a tray in the oven at 170F.
Wash your lids and set them aside in a clean place. You no longer need to simmer lids in water to keep them sterile. Woot!
Making the jam
Rinse the strawberries. Remove the tops, cut in half (or quarters for large berries), and place in a bowl. Gently mash with a potato masher or pastry cutter until it yields 2.5 cups of mashed berries.
You can also “cheat” and start with Strawberry Puree or Frozen Strawberries in Syrup if you already have some on hand.
Add the rhubarb to a heavy-bottomed saucepan with 1/2 cup of water. Cook on medium heat, stirring often until the rhubarb softens. You’ll need about 4 cups of fresh sliced rhubarb to yield 1.5 cups of cooked rhubarb. Stir in the mashed strawberries and continue to cook the mixture until the fruits are combined.
In a small bowl, combine 1/2 tsp calcium powder (in the Pomona’s Pectin box) with 1/2 cup cool water to create calcium water.
In a separate bowl, combine sugar and pectin. Set aside. To prevent clumping, Pomona’s must be mixed with your sweetener before being added to the fruit.
Add the lemon juice and calcium water to the pot with the rhubarb and strawberries, stir. Add the sugar/pectin mixture, and bring to a rolling boil. Stir constantly for 3 minutes, turning down the burner to medium if the jam starts popping. Pro tip: actually set a timer and stir for the full three minutes. The constant stirring prevents the jam from burning, and the cooking time is important to help the jam set.
Pro tip: a rolling boil means no amount of stirring will stop the bubbling. Use a long spoon or spatula to avoid any jam popping onto your hand.
At this point, turn the burner under the canner back up to high and get that water boiling again.
Remove the jam pot from heat, and stir gently for 5 more minutes. At the end of the 5 minutes, remove any foam that remains.
Using the funnel and a ladle, add the jam to your prepared jars, leaving 1/4 inch of headspace at the top. Headspace is the amount of room between the top of the food, and the rim of the jar.
Using a wet clean rag, wipe the rim to make sure there isn’t any sticky jam on there.
PRO TIPS/RECIPE NOTES
- If you prefer a tarter jam, use 2.5 cups of cooked rhubarb and 1.5 cups of mashed strawberries.
- You can keep an opened jar in the fridge for a month. Sealed jars are safely stored at room temperature for up to a year.
- Jam is best when made in small batches. Avoid doubling or tripling the recipe.
- The mixed calcium water will last for three months in the fridge. Shake well before using it for other recipes like Low-Sugar Strawberry Jam.
- You can reduce the sugar to 1 cup if desired but you would need to cook the jam down for 8 minutes instead of 3.
Strawberry Rhubarb Jam (Low Sugar)
Ingredients
- 2.5 cups strawberries {mashed}{~4 cups fresh}
- 4 cups chopped rhubarb {~1.5 cups cooked}{~3 large stalks}
- 1/2 cup water {for rhubarb}
- 2 tbsp bottled lemon juice
- 3 tsp Pomona's Pectin
- 1/2 cup cool water {for calcium water}
- 3 tsp calcium water {from Pomona's Pectin box}
- 1.5 cups sugar
Equipment
Instructions
Prep for Canning
- Prepare water bath canner by filling it halfway with water, and setting it on the stove. Turn the burner to high. Once it reaches a boil, reduce it to simmer. You want to keep the water hot so that everything is ready when the jam is.
- Wash and clean your jars. Fill with hot water or keep them warm in a clean dishwasher or oven.
- Wash your lids and set aside in clean place.
Making the Jam
- Rinse the strawberries. Remove the tops, cut in half or quarters, and place in a large bowl.2.5 cups strawberries
- Gently mash with a potato masher or pastry cutter until it yields 2.5 cups of mashed berries.
- Add the clean chopped rhubarb to a heavy-bottomed saucepan with 1/2 cup water.4 cups chopped rhubarb, 1/2 cup water
- Cook on medium heat, stirring often until the rhubarb softens.
- Stir in the strawberries and continue to cook the mixture until the fruits are well-combined.
- In a small bowl, combine 1/2 tsp calcium powder from the Poman's Pectin box with 1/2 cup cool water to create calcium water.1/2 cup cool water
- In a separate bowl, combine 1.5 cups of sugar and Pomona's pectin. Set aside.1.5 cups sugar, 3 tsp Pomona's Pectin
- Add 2 tbsp lemon juice and calcium water to the pot with the rhubarb and strawberries, stir.2 tbsp bottled lemon juice, 3 tsp calcium water
- Add the sugar/pectin mixture, and bring to a gentle rolling boil.
- Stir constantly for 3 minutes, turning down the burner to medium if the jam starts popping.
- Remove from heat and continue stirring for 5 more minutes. At the end of the 5 minutes, remove any foam that remains.
- At this point, turn the burner under the canner back up to high and get that water boiling again.
Canning the Jam
- Using the funnel and a ladle, add the jam to your prepared jars, leaving 1/4 inch of headspace at the top. Headspace is the amount of room between the top of the food, and the rim of the jar.
- Using a wet clean rag, wipe the rim to make sure there isn't any sticky jam on there.
- Place a clean lid on the jar and then a ring. Tighten the ring to fingertip tight.
- Using canning tongs, add jars to the boiling water, and put the canner lid on. Pro tip: you must have at least 1 inch of water over the tops of the jars for safe canning.
- Process (boil) for 10 minutes.
- Remove the canner from heat, and let sit for 5 minutes.
- Remove the jars and place them on towels on the counter undisturbed for 12-24 hours.
- After everything has cooled, check the seal by pushing down on the middle of the lid. If it doesn't give way, it's sealed. If the lid bows a little bit, put that in the fridge and use it within 3 weeks.
- Label the sealed jars, and store in a cool dark place for up to a year.
Notes
- Makes 5, 8 oz jars.
- Will last for 1 month in the fridge or 12 months sealed and at room temperature.
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The Pomona’s pectin says to use 1/2 to 3/4 teaspoons (tsp.) of pectin per cup of mashed fruit and 1/2 to 1 tsp. of calcium water per cup of fruit. If I am reading the recipe correctly, I believe it is calling for tablespoons (tbsp.) instead of teaspoons for the pectin and calcium water. It that to make the jam firmer?
I took a second look at it and it appears to be a typo. Thank you for catching that – it should be tsp! I’ve updated it in the post.
Sounds delicious. I usually make freezer jam and both your recipe and mine for freezer specify mashing the berries instead of using a food processor. Why?
I believe to keep some of the berries intact so the “gel” happens. If you processed them too much, you’d essentially be making really watery jelly that wouldn’t set. I believe in most cases, “real” jelly requires a ton more sugar too.