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When it comes to jam, there are rules. According to the FDA’s legal designation, jam can only come from one type of fruit, whereas compotes and conserves can be made with additional fruits (often dried ones) or nuts (jellies are made of juice or syrup, without chunks of fruit). But if it’s made from a vegetable, even just one, can it still be called jam?
Rhubarb is an ingredient with an identity crisis. If it’s a vegetable, why is it always treated like a fruit? Maybe it’s because it comes up before the berries and tree fruits have even set their blossoms, when dessert makers of yore had few other choices? Maybe it’s the rich, carmine hue of rhubarb’s stems, instantly drawing the mind to sweet cherries and plums. Or maybe it’s just because sweet and sour have always been a winning combination.
Sourness is rhubarb’s superpower, but it’s also a major strength of sorrel — a weedy little plant that will happily spread through the shady spaces of the garden if left to its own devices (ask me how I know). The name “sorrel” means sour, but even though they’re both high in vitamin C, sorrel and rhubarb primarily get their sourness from oxalate, not ascorbic acid.
Oxalate (or oxalic acid) is named after oxalis, a genus to which the diminutive and ubiquitous Pacific Northwest plant, wood sorrel (Oxalis oregana) belongs. Wood sorrel isn’t a true sorrel, though; it’s in its own family (Oxalidaceae) instead of the buckwheat family (Polygonaceae), to which rhubarb, true sorrel (garden, blood or otherwise), Vietnamese coriander and weedy docks belong.
And thanks to this oxalate (of which both the rhubarb and blood sorrel have plenty), this compote is an alimentary exclamation point, with a bright and sour flavor that punches through its sweetness like the Kool Aid Man, making it a sublime foil for ricotta pound cake, vanilla ice cream, or even plain Greek yogurt. Don’t worry too much about whether or not you should call it jam, compote or conserva (maybe since rhubarb is a vegetable, this is a stew?).
Makes about 1 pint of compote
A word of warning: Oxalate’s sourness is nice on the tongue, but in some plants (rhubarb leaves and raw sorrel, for example), oxalate is highly soluble. It’s absorbed by the gut and bonds with the calcium in your body. In high enough concentrations, it can form calcium oxalate crystals, which turn into kidney stones. (Fun fact: parsley is actually higher in oxalate than rhubarb, but because of its other chemical constituents, the oxalate in this herb is less likely to be absorbed by the body.) If you’re prone to kidney stones, maybe wait for strawberry season instead, but most folks should be able to enjoy these ingredients as a seasonal delicacy without issue.
Another note: Blood sorrel has a much thinner stem than rhubarb, but its sanguine color and tart flavor make it a perfect match for its burlier cousin. To use it here, strip the leaves off the stems with your fingers (you can chop them up for salad) and finely dice the stems so they cook down to tenderness like the rhubarb. Don’t worry about adding pectin to this compote — even though rhubarb and sorrel aren’t that high in pectin, the acidity provided by oxalate and a squeeze of lemon will gelatinize the pectin and tighten these preserves right up.
Ingredients
2 cups chopped rhubarb and blood sorrel stems (I used 3 rhubarb stalks plus 10 blood sorrel stems)
¼ cup water
1 ½ cups sugar
½ teaspoon cardamom
1 tablespoon lemon juice (or ⅛ teaspoon citric acid)
Instructions
- Place all the ingredients in a small, heavy-bottomed pot over medium heat. When it begins to boil, reduce the heat to low and simmer until it looks and feels like jam, about 20-30 minutes. How will you know it’s ready? It’ll coat the back of a spoon and if you drip a little on a cold plate, it’ll be gelled and jammy.
- Taste, add more sugar or lemon juice according to your preference, pour it into a jar and affix the lid tightly. You can scale this recipe up for canning, or allow it to cool completely on the counter before stashing it in the fridge (it’ll be good for months).
