Blueberry-Plum Butter Recipe (in the slow-cooker)

This slow-cooker blueberry plum butter gives you an easy, hands-off way to turn fresh summer fruit into a silky, spreadable treat. You start by pureeing the fruit, then let the crock pot slowly simmer it down until it thickens beautifully. A touch of sugar and lemon brighten the flavor, and you can store it in the fridge, freezer, or process jars for shelf storage. Expect deep, intense fruit flavor and a texture similar to ketchup that’s perfect for spreading on toast or stirring into yogurt. Plus, it’s a recipe that works while you’re busy doing other things—win-win!

Bright, jammy, and bursting with flavor, this slow-cooker blueberry plum butter is a fantastic way to capture the best of summer fruit without fuss. You simply puree the blueberries and plums, then let the crock pot work its magic, gently reducing the mixture until it thickens into a luscious spread. During the last hour of cooking, you add sugar along with fresh lemon zest and juice to really lift and round out the flavors. For an ultra-smooth finish, give it one last blend with an immersion blender before packing it up.

Plan for a good few hours of slow cooking: after the first hour, prop the lid open just a bit so steam can escape for better reduction. Then cook on high for 4 to 5 hours or on low for 6 to 8 hours, stirring about once every hour so nothing sticks or scorches. This slow cooking brings out all the fruit’s natural sweetness and deep flavor, and keep in mind the butter will keep getting firmer as it cools down.

By the time you’re done, you’ll have:

• A vibrant mix of concentrated blueberry and plum flavor, brightened with fresh lemon zest and juice.
• A thick, spreadable fruit butter with a ketchup-like consistency that firms up nicely as it cools.
• Enough buttery goodness to fill around 6 half-pint jars or 3 pint jars, ready to be refrigerated, frozen, or canned for long-term storage.

This is such an easy way to turn fresh summer berries and plums into something that works perfectly on morning toast, dolloped into yogurt, or saved for baking later—all while you get on with your day.

Ingredients You’ll Need

• 5 pints fresh blueberries
• 4 large ripe plums
• 2 cups organic golden cane sugar (you can swap in white sugar if you like)
• Zest and juice of 1 organic lemon

Slow-Cooker Method

1. Spread blueberries on a tray and pick through to remove stems, leaves, and debris.
2. Rinse blueberries and plums under cold water and drain well.
3. Cut plums in half and remove pits.
4. Place blueberries and plums in a food processor or blender and puree until smooth.
5. Pour the fruit puree into the slow cooker.
6. Cover the slow cooker and set to high (or set to low for 6–8 hours).
7. After the first hour, stir the fruit mixture and prop the lid open slightly to let steam escape.
8. Cook on high for 4–5 hours or on low for 6–8 hours, stirring about once every hour to prevent sticking or scorching.
9. In the last hour, stir in the sugar, lemon zest, and lemon juice.

10. Continue cooking until the mixture reaches a ketchup-like thickness.

    

11. Use an immersion blender and blend until ultra-smooth, if desired.
12. If canning, sterilize jars by boiling them for 10 minutes and keep lids and rings warm in simmering water.
13. Fill hot fruit butter into hot jars, wipe rims clean, and seal with warmed lids and rings.
14. Process sealed jars in a boiling water bath for 10 minutes.
15. Carefully remove jars and let them cool completely without disturbance, then check seals the next day.

Tips for Perfect Butter

• Keep the slow cooker lid cracked after the first hour to help the fruit mixture reduce nicely and avoid sogginess.
• Stir your fruit butter roughly every hour to prevent hot spots and sticking; slow cookers all heat a little differently, so adjust your timing to suit your machine.
• The finished texture should resemble ketchup—thick and spreadable—and it’ll set more as it cools, so don’t worry if it seems a bit loose straight from the cooker.
• If you love silky smooth fruit spreads, just blitz it one more time with an immersion blender after cooking is finished—think the velvety finish of Homemade Blackberry Butter.
• Golden cane sugar adds a wonderfully rich caramel undertone, but plain white sugar works just fine too. Just keep in mind switching to different sweeteners might change flavor and texture a bit; for a honey-sweetened approach (and canning tips), see Vanilla Honey Peach Butter.
• When freezing jars, leave about a 1/2 inch gap at the top to allow for expansion without cracking.

Mix-Ins and Substitutions

• For a warm, cozy twist, stir in 1/2 to 1 teaspoon ground cinnamon and a pinch of nutmeg during the last hour of cooking. This variation is inspired by Marisa McClellan’s classic version.
• Want pure blueberry flavor? Skip the plums and use 8 cups of just blueberry puree for an intensely bright spread. Prefer a plum-only version instead? Try this Vanilla Bean Plum Butter.
• Feel free to swap plums with peaches, raspberries, or strawberries to create your own fruit butter blends that fit your taste.
• Try adding part maple syrup for a hint of natural sweetness and complex flavor, but remember that liquid sweeteners may alter the texture and preservation.
• Want less fruit butter? Just halve the ingredients to make a smaller batch that suits your needs.

Storage and Canning

Refrigerate opened or unprocessed fruit butter for up to two weeks to keep it fresh and tasty.

Freeze your fruit butter in jars or containers for up to six months. Don’t forget to leave about 1/2 inch headspace so it has room to expand without cracking. Fruit butters like Pear Vanilla Butter freeze especially well.

If canning, process your filled jars in a boiling water bath for 10 minutes. Let them cool overnight and store sealed jars in a cool, dark place for up to six months. Once opened, transfer to the fridge and use within two weeks. The same process works for other high-acid fruit spreads like Chai Spiced Apple Butter.

To warm it back up and make it extra spreadable, gently heat the fruit butter on the stovetop or in the microwave before serving.

Common Questions

Q: Can I use frozen berries instead of fresh? A: Absolutely! Just thaw them first and drain any extra liquid. You might need to adjust cooking time a bit since moisture levels can vary.

Q: Do I need to add pectin? A: Nope. This blueberry plum butter cooks down until it’s naturally thick and spreadable, so extra pectin isn’t necessary. For another naturally thick, pectin-free fruit spread, try our Mango Butter.

Q: Can I leave out the plums? A: Yes, you can make a blueberry-only butter by using about 8 cups of pureed blueberries.

Q: Is it okay to change the amount of sugar? A: You can reduce sugar to suit your taste, but this recipe balances flavor and texture well. If you want to can your butter safely, stick to tested proportions or plan to store lower-sugar batches in the fridge or freezer. For a fruit butter with balanced sweetness and spice, see this spiced pear butter recipe.

Q: My slow cooker tends to scorch the fruit. What should I do? A: Try turning your cooker down to low heat and stirring more often. Some models cook hotter than others, so adjusting your time and stirring frequency helps prevent burning.