I always get excited when rhubarb season hits because it means I can finally whip up a batch of this recipe for raspberry rhubarb jam. There's something about that specific window in late spring and early summer when the rhubarb is still tart and crisp, and the first raspberries are starting to show up at the farmer's market. If you've never tried these two together, you're missing out on one of the best flavor pairings in the world of preserves. The rhubarb brings a sharp, punchy acidity that cuts right through the floral sweetness of the raspberries, making a jam that isn't just "sugar-sweet" but actually has some depth to it.
I used to be a bit intimidated by jam making. I thought you needed a chemistry degree and a kitchen full of specialized equipment. It turns out, you really don't. While you can get fancy with pressure canners and pH strips, a simple small-batch approach is much more relaxed and way more fun. This recipe is meant to be approachable, even if you're just working with a standard pot on a normal stove.
Why This Combo Works So Well
Raspberries are delicious on their own, but they can be a little one-note when you turn them into jam. They're very sweet and have that signature berry fragrance, but they sometimes lack the "zing" that makes a preserve stand out. That's where the rhubarb comes in. Rhubarb is essentially a vegetable that thinks it's a fruit, and its natural sourness acts like a spotlight for the raspberry flavor.
When they cook down together, the rhubarb softens into these lovely little ribbons that add a bit of texture, while the raspberries break down into a beautiful, deep red syrup. The color is incredible—it's like a jar of melted rubies. Plus, both fruits have a decent amount of natural pectin, though I usually add a bit of lemon juice just to make sure it sets properly without having to boil it for an eternity.
What You'll Need Before You Start
For this recipe for raspberry rhubarb jam, you don't need a massive list of ingredients. In fact, keeping it simple is usually better.
- Rhubarb: You'll want about a pound of fresh rhubarb. Look for stalks that are firm. The redder they are, the prettier the jam will be, but green stalks taste just as good.
- Raspberries: A pound of raspberries is perfect. Fresh is great, but honestly, frozen ones work just fine if that's what you have.
- Sugar: I usually go for about 3 cups of granulated sugar. I know it sounds like a lot, but sugar is what preserves the fruit and helps it set.
- Lemon Juice: Use fresh lemon if you can. It adds a bit of brightness and the acidity is crucial for the pectin to do its job.
- A tiny bit of butter: This is an old trick to keep the foam down while the jam boils. It's optional, but it saves you from having to skim the top constantly.
Getting the Fruit Ready
First things first, you've got to prep your rhubarb. Trim off the ends and any leaves (don't eat the leaves, they're toxic!). Slice the stalks into small pieces, maybe half an inch thick. If you have really thick stalks, slice them down the middle lengthwise first.
Give your raspberries a quick rinse and pat them dry. Then, toss both the rhubarb and the raspberries into a large, heavy-bottomed pot. Add your sugar and lemon juice. I like to let the mixture sit for about thirty minutes to an hour before I even turn on the heat. This is called macerating. The sugar draws out the juices from the fruit, creating a natural syrup. It helps the rhubarb soften more evenly and prevents the sugar from scorching when you start the stove.
The Cooking Process
Once your fruit looks nice and juicy, turn the heat to medium-low. Stir it gently until all that sugar has dissolved. You don't want to see any grainy bits on the side of the pot. Once it's fully liquid, crank the heat up to a medium-high.
You're looking for a "rolling boil"—that's a boil that doesn't stop even when you stir it. This is where the magic happens. You'll notice a lot of foam rising to the top. This is totally normal. If it bothers you, drop in that tiny knob of butter I mentioned earlier; it'll settle the bubbles right down.
Keep stirring fairly often. You don't want the bottom to burn, which can happen quickly once the syrup gets thick. The whole process usually takes about 15 to 20 minutes of boiling, but it depends on how much water was in your fruit.
Testing the "Set"
One of the trickiest parts of any recipe for raspberry rhubarb jam is knowing when it's actually done. If you undercook it, you have delicious fruit sauce (great for ice cream, but not jam). If you overcook it, it becomes tacky and hard.
I use the cold plate test. Before I start cooking, I put a couple of small saucers in the freezer. When I think the jam is getting close—it'll look glossy and the bubbles will start to sound "heavier"—I pull out a cold plate. Drop a small spoonful of jam onto the plate and let it sit for a minute. Then, push the edge of the jam with your finger. If it wrinkles up, it's done! If your finger just slides through a liquid puddle, let it boil for another few minutes and try again.
Canning or Just Chilling?
Now you have a choice. If you're planning on eating this within a few weeks, you can just pour the hot jam into clean jars, let them cool to room temperature, and stick them in the fridge. It'll stay fresh for about three weeks, maybe a month if you're lucky.
But if you want to keep this on your shelf for the winter, you'll need to do a quick water bath. This just involves boiling the filled and capped jars in a big pot of water for about 10 minutes. It seals the lids and kills off any bacteria. There's something so satisfying about hearing that little "pop" sound as the jars cool down and the vacuum seal forms.
A Few Tips for Success
Don't be tempted to double the batch in one pot. I know it seems like a time-saver, but jam needs a lot of surface area for the liquid to evaporate. If the pot is too full, it takes way longer to reach the setting point, and the fruit can lose its bright flavor and turn a dull brown. It's better to do two separate batches if you have a ton of fruit.
Also, don't skimp on the sugar. I know everyone wants to be healthy, but sugar isn't just a sweetener here; it's a structural ingredient. If you want a low-sugar jam, you usually need to buy a specific type of low-methoxyl pectin, otherwise, you'll just end up with a runny mess.
How to Enjoy Your Jam
Obviously, this is killer on a piece of sourdough toast with way too much butter. But don't stop there. This recipe for raspberry rhubarb jam is amazing as a swirl in plain Greek yogurt or oatmeal. If you're feeling fancy, try using it as a filling for thumbprint cookies or spreading a layer of it between cake layers.
My personal favorite way to eat it is on a cheese board. The tartness of the rhubarb makes it go incredibly well with a sharp cheddar or a creamy goat cheese. There's just something about that sweet-salty-tart combo that hits all the right notes.
Making your own jam might seem like a lot of work, but once you taste the difference between this and the store-bought stuff, there's no going back. It tastes like actual fruit rather than just flavored corn syrup. Plus, having a few jars of this in the pantry feels like you've successfully bottled up a little bit of summer to enjoy whenever you want. Happy cooking!