June Can Jam: Slow Cooker Blueberry Butter

washing blueberries

Well kids. The Tigress Can Jam challenge this month was anything that ended in “erries” and since this is my summer of fruit butters, I have made a batch of blueberry butter. Last weekend, my friend Shay and I took a little drive out to my favorite blueberry pickin’ spot in South Jersey and spent a couple of hours rattling berries from branches, filling our buckets and bellies.

However, the true treat of the day came when we rounded the corner of the farm stand in order to pay for our hauls. Standing right in front was my cousin Amy, out for a day of picking with her partner and two of their grandkids. We had one of those truly lovely moments, when you gape open-mouthed for a moment before laughing and falling into hugs.

blueberries in the Vitamix

Once home with my seven and a half pounds of berries, I spent several days eating them popcorn-style out of bowls, before hunkering down and making a preservation plan for the rest. Last year I called blueberry my foundational jam and that’s still a phrase that feels correct. I will always love that simple jam (in fact, I still have some from last year), but this time around I wanted to try something slightly different.

Originally I had planned to make a blueberry butter spiked with a hint of lavender, but this week was busy enough that I didn’t have a chance to get to Reading Terminal Market and that’s the only place close by where I can get food-grade lavender. So I went simple and stuck with my mom’s preferred flavor profile of lemon zest, cinnamon and just a bit of nutmeg.

drippy slow cooker

Lately, I’ve been turning to two gadgets to make my preserving work just a little bit easier to accomplish. The first is my trusty Vita-mix. I grew up with the vintage chrome version of this incredible blender and so during wedding time last year, made it a priority to dedicate some of our gifted resources to acquiring my own.

While I had an inkling that it had the potential to be a transformative piece of equipment, I had no idea how it would revolutionize my jam making. Here’s what makes it so special: When you run it on very low speed, it doesn’t puree the fruit. It just chops it up into small bits, which coincidentally, are the absolutely perfect size for jams and butters. I know it’s a little bit unfair to rave about something that’s so darned expensive, but really, this thing has changed my life for the better.

half pint of blueberry butter

The other small electrical appliance (that happens to be on the very other end of the cost spectrum) that I’m using all the time these days is my ancient, $3-at-a-thrift-store slow cooker. I’ve found that older slow cookers are far superior to newer ones, because they cook at lower temperatures. Truly, food safety regulations have made it so that what was once the high setting on the old pots is now the low setting on the new ones (you should never be able to achieve a boil in one of the pots from the seventies or eighties). And when you’re cooking a butter, you want to cook it as low and slow as you can. Slow cookers are truly perfect for this.

This particular butter reminds me a bit of blueberry pie, which makes it a winner in my book. Tomorrow morning, I’m having some friends over to do a little fruit butter tasting (in recent days, I’ve also made apricot butter and sweet cherry butter). We’ll see if they like the blueberry version as much as I do.

Slow Cooker Blueberry Butter

Yield: Approximately 3 1/2 Pints


  • 8 cups of pureed blueberries
  • 2 cups sugar
  • 1 lemon, zested
  • 2 teaspoons cinnamon
  • 1/2 teaspoon grated nutmeg


  1. Put the pureed blueberries in a slow cooker. Place a lid on the pot and turn it on to low. After about an hour, give it a stir. At this point, you want to use something to prop the lid a bit. I found that laying a wooden spoon across the rim of the cooker and then placing the lid on gave it just enough room to let the steam evaporate.
  2. My blueberry butter spent about six hours in the slow cooker (from 5:30 p.m. when I got home from work, until 11:30 p.m. when I canned and processed it). At the beginning of hour five, I added the spices, lemon zest, and the sugar, removed the lid completely and turned the heat up to high, in order to speed the cooking down.
  3. Once it’s cooked down sufficiently*, pour into jars (leave a good 1/2 inch of head space), wipe rims, apply lids and screw on bands. Process in a boiling water canner for 10 minutes. Eat on fresh scones and store unopened jars in a cool, dark place.


*When the cooking process is done, you can puree with an immersion blender or (carefully) in a regular blender, for a smoother product. It depends on whether you like your butters a bit chunky or very smooth.


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170 responses to “June Can Jam: Slow Cooker Blueberry Butter”

  1. As I do not have a boiling water canner but do have a Dutch oven: Is it OK – or possible – to put the jelly jars in the Dutch oven? If so, do the jars go right on the bottom of the pot or do they need a rack? Should the jars be touching each other – touching sides of the pot? How much water should be in the pot? An inch over the top of the sealed jars? After they are processed, should I handle them as I do for tomatoes processed in the pressure cooker – remove to clean folded towel to cool & seal collapses & screw band is tightened after contents cools a little? Can the jars be frozen? (it would not be possible to find a cool spot in the house, unless 75 degrees is considered cool) I would love to give these as Christmas gifts, as well as have some for myself. Many thanks for your help.

  2. Can you can these? i made some pineapple butter and now i have about 10 jars and im wondering what to do with it can it, freeze it or what?

    • There are canning recipes written into the recipe, so yes, you can can this one. I’ve never made pineapple butter, so I don’t know if it can be canned.

  3. Wow sorry if that sounded snakry lol didn’t relise that till i re-read it after i posted :/ im new to canning and not sure if you need some special preservative to make sure it safe.

  4. I’ve a bunch of Saskatoon berries that I picked this Summer.. at the time, I’d never canned a thing in my life, or thought that I would! ..fast forward 2 months later, and its a whole other story.

    This sounds like a fantastic way to use some of those berries, though I’m wondering if I should just wait until next summer, or if my frozen ones would be okay?

    If you’re not familiar, Saskatoons are similar to Blueberries. 🙂

  5. Great recipe! I just happen to have an old (smaller) slo cooker, perfect for this.
    I’m always confused on the conflicting advice on how much space to leave at top of jar. Some recipes say fill it right up, as this STOPS any mould getting in, others the exact opposite! Which one is it? It can’t be both! Thanks.

  6. I hope some ones on here soon. LOL I made this 2 yrs ago and loved it. I just pureed my berrys and put in the C.P. They have been in there an hour. I stirred them and it is REALLY thick. I cant remember if that’s normal? its almost like jam now. will it cook down to get some liquid in it or did I puree to much? Please help I love this recipe. Thank-you.

  7. You have pretty much come to my rescue with this recipe, as I have 20 lbs. of blueberries and a double crock pot that is begging to be put to a good use. I may try adding a little vanilla bean (and maybe some lemon verbena!) to the mix and see how that goes too. Thank you sooooo much!!!

  8. My butter didn’t set into butter. It’s more like a jam. Followed directions exactly and after 6 hrs when it hadn’t set I moved it to the stove and simmered for another 40 minutes. Any ideas on what to do to help it set? Or should the consistency just be like a jam? I kind of pictured it being super thick like apple or pumpkin butter.

    Any suggestions would be appreciated as I was going to do another batch w/vanilla bean in it! Thanks so much.

    • Tami, cooking times vary for products like this. Just because mine took six hours doesn’t mean that yours will be done in exactly that much time. Thought it’s been awhile since I made this butter, I seem to recall that it doesn’t get quite as thick as apple or pumpkin butters do.

      • Wow – thanks for the quick reply, Marisa! And for helping me get a better understanding of the expected consistency. I made it last night and can’t wait to taste it. Just picked up your book and love it 🙂

  9. I love the blueberry butter recipe, i realized i dont have the lemon on hand as i started this project, arrgh, but i think i will just improvise with this trial batch and use orange zest and juice, i love the combination of oranges and blueberries. wish me luck!

  10. Hi! I found your slow cooker blueberry butter because I was looking for slow cooker raspberry butter. Do you know if this can be done? Do I have to use lemon or pectin? Can’t I just cook it down using only my raspberries and a little water and then process it in a boiling water bath?

    I look forward to hearing from you.

  11. Marisa – do you think I could do this recipe with saskatoon berries? I don’t see any saskatoon berry recipes on your site but thought you’d probably know if I should adjust anything… Add some lemon juice maybe?

    • I have never used saskatoon berries, so I really don’t know. However, according to this article, they have a low enough pH that they can safely be canned in a boiling water bath. So I would give it a shot!

  12. This is my first time canning so I don’t know if I am really doing everything correctly. I had to cook my Blueberries on the stove. Now, after I put the sugar and spices in, let it cook for an hour is was still gritty. Is it supposed to be like this?

    • It should not be gritty and I’m not exactly sure why it is. Did you puree it really well with an immersion blender? Did the sugar fully dissolve? Were the blueberries totally clean?

  13. I have that same slow cooker. LOL. I appreciate your thoughts on old vs. new. I can’t wait to try this recipe now.

  14. This blueberry butter was fantastic and a nice substitute for blueberry jam. I decided to make blueberry ice cream using the blueberry butter and turned out amazing! Possibly the best flavored ice cream I’ve ever had. Only used 1 1/2 pints of the butter for a 10 yolk, 3 c. milk, 3 c. cream recipe and it added intense flavor. I did add another 2 c. of sugar to the ice cream recipe in addition to what went into the butter but it wasn’t too sweet, just right. A must try!

  15. Just canned this using 1/2 inch head space as recommended in the recipe. I was sure this would win at the county fair. Unfortunately I checked the local fairs guide lines after canning and they require 1/4 inch head space.

  16. I’ve never canned before and am still too afraid to try. Once cooled, can I put this in freezer bags and freeze?

    • Freezer bags aren’t really a great vessel for jam. They’d do better in a small freezer-safe containers.

  17. Hi Marisa,

    I just made a batch of your heavenly blueberry butter recipe from your Food in Jars book. I’ve received many compliments about it and would like to make a bunch of jars for Christmas gifts but noticed the recipe recommends keeping it stored up to six months. Is there any wiggle room with this timeline?

    Many thanks,

    • Hi Again – I just found the answer to my question on another Food in Jars web page. Thanks for all the good information you provide to us canners.

  18. I made pear butter few years ago, and if you want a treat have pear butter with almond butter on your Belgium waffle. So good! I am excited to make blueberry butter. So thank you for this post and idea. I have enjoyed reading thru the comments. Keep creating! 🙂

  19. You are an inspiration and have gotten me interested in canning in a way I never expected! I have cross-referenced a few of your butter recipes and think I’ve figured this out, but is the lemon zest necessary for acidity (I don’t even know if the zest technically has acidic properties like juice does)? I’d love to make a batch but would prefer to omit the lemon, if it’s safe. Thank you for helping with my newbie questions!

    • The lemon is just there to balance the flavor. It’s not necessary for safety. You are welcome to omit it.

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