This rhubarb jam recipe makes a pretty small batch, but it’s easy to scale up as needed. However, unless you are the proud owner of a super productive rhubarb garden, I highly recommend sticking to the smaller amount. After all, smaller batches of jam come together much more quickly than large batches. Why is that?

Well, jam-making is all about boiling off moisture from the fruit. With a larger vat of jam, you have to let it bubble away for much longer to get enough water to evaporate (sometimes as long as an hour!). I’d personally much rather just spend a quick 15 minutes whipping up a jar every once in a while.

But it’s your call! This recipe has you covered whether you want to make enough for the whole neighborhood or enough for that little gap in your fridge door.

Jump to the recipe to hit the ground running, or read on for a few helpful jam tips (and check out my other rhubarb recipes, including rhubarb cookies featuring this very jam):

Rhubarb jam best practices

1) Don’t add much water

Some recipes for jam suggest adding several cups of water at the beginning of the process. I can almost get behind the idea—a bit of water helps the fruit soften faster and start to break down. However, as we know, the whole point of jam-making is to cook off as much water as possible. Adding a ton of water in the beginning is just setting us up for a needlessly long process.

Instead of starting the jam totally dry on the stove, I use the following technique instead:

Add 1 Tbsp of water to the bottom of the pot, followed by the fruit and sugar. Then without stirring, let it simmer for a few minutes. The water gets things going without adding much moisture. If you were to stir it before things start simmering, the sugar will start to grab onto some of that water, slowing things down a bit.

2) Use a wide pot or pan

The wider the pot/pan, the faster your jam will cook. If you use a super narrow saucepan, it will take longer for water to cook off. Surface area is your friend. Use a wide skillet, dutch oven, or other pan with a nice amount of floorspace.

3) Most “freezer plate” advice is slightly wrong

The freezer plate method of checking jam doneness is fantastic, but I think most people get it like 5% wrong (and unfortunately, it’s the most important 5%).

Most videos/recipes will tell you to place a blob of jam on a frozen plate, and then drag your finger across it. According to these guides, if it doesn’t fill back in, it’s done. But this is unfortunately not a reliable cue. Even if your jam is quite underdone, it will often pass this test.

Instead, move the blob of jam around the plate a bit with your finger or a spoon to fully chill it and judge its consistency. Once chilled, does it have a thick, sticky consistency? Or does it feel more like a syrup than a jam? Would you spread that blob on toast, or would you drizzle it into an old fashioned?

4) Scale the sugar up slightly if you want it to keep longer

I love my jam sweet, but not so sugary that it waters down the flavor of the fruit. But, unfortunately, a sweeter jam will keep longer in the fridge.

Traditional recipes usually go for a 1:1 ratio of fruit to sugar (by weight). So for this amount of rhubarb (300g), that would be 1 1/2 sugar (300g)—1/4 cup more.

I personally prefer the flavor of this recipe’s ratio, which is by no means low-sugar, but if you want your rhubarb jam to last longer than a couple weeks, you might wish to go with the full amount of sugar. Discard if it starts to grow mold (mold has roots!), smells like alcohol, or starts to look slimy.

I prefer storing anything I don’t plan to use in the next week or two in the freezer, moving to the fridge as needed. I usually split this recipe in half, storing a small jar in the freezer and a small jar in the fridge.

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