One of the most poignant and bittersweet memories in my childhood is of steaming vats of water in an already-steamy, un-airconditioned rustic kitchen, used first to slip tomatoes of their paper-thin skins and then to boil Ball jars filled with said tomatoes, chopped, until the satisfying “pop” of a vacuum jar meant they were safe to store. These bright red jewels (and others, like blackberry jam, and strawberry, too) lined the shelves of the stone steps that led to a dirt basement under the kitchen and ensured a winter’s worth of sauce and a fresh burst of summer flavor on even the bleakest days.

I was a reluctant helper. It seems the sauce always popped when I passed by, burning my skin, or the tomatoes were stubborn in their skins. Mostly I passed through the kitchen as quickly as possible, fleeing to books or shady spots on our wooded property, ever-mindful of snakes.

These days I understand better the value of those jewel-toned jars.

They represent plenty, excess even, so much abundance that it must be stored away. They guard against want on short days with not much sun and preserve a summer’s effort so that you can slide into those lazy days when there is two feet of snow on the ground outside the window.

Blackberry jam is one of the first products of early summer, ready before tomatoes bent the shoulder-high tomato plants under their weight. Gathered carefully, ever mindful of snakes that enjoyed resting on their ample leaves, blackberries turned into sweet-tart blackberry jam are one of life’s best pleasures.

My lovely friend Martha of Full Moon Acupuncture has happy blackberry vines in her Baltimore backyard and is generous with them This blackberry jam is made with only three ingredients: blackberries, sugar, and lemon juice. Because blackberries are naturally high in pectin, it is not necessary in this recipe for low-sugar blackberry jam.

The formula for blackberry jam is simple if you want a stereotypical batch: weigh your blackberries and use an equal amount of sugar. For me, this results in sickly-sweet jam that tastes more of sugar than sunshine-y blackberries. For this recipe, I weighed my berries and used half that amount of sugar. You could use even less for a low- or no-sugar blackberry jam, but that would take longer on the stove.

Low-Sugar Blackberry Jam

(makes five half pints, plus a little leftover)

Weighing your blackberries is the best option here, as cup measurements are challenging. I use half as much sugar as blackberries – it’s a good formula for a juicy, blackberry-forward, low-sugar blackberry jam.

Ingredients

Just over six cups of blackberries, by weight (50 ounces)

Just under 3 cups of sugar, by weight (20 ounces)

Two tablespoons lemon juice

Method

If you are planning on water bath processing your jam, get your jars ready first. Wash jars and lids in warm, soapy water while you bring a stockpot of water to boil on the stove. Boil clean jars for two minutes, then move to a clean dish towel. Dip lids, ladles, and anything else you will use in the canning process into the boiling water and set aside.

Put a clean plate in the freezer to test the blackberry jam for doneness. This will become clear soon.

Place blackberries, sugar, and lemon juice in another large pot (leave lots of headspace for the jam to foam). Mash slightly and bring to a boil.

Play something nice on the radio, or load up a podcast. Lower heat to medium low, and stir as the jam boils/simmers. Stir the foam down as it rises.

Over time, your jam will stop foaming, become glossy, and thicken substantially. This could take between 20 to 30 minutes. Be patient. Be attentive. Take this as an opportunity to be mindful.

To see if your jam is ready, remove the frozen plate from the freezer and spoon a bit of jam onto it. Let cool for a couple minutes, then drag a finger through the jam. If it makes a path that does not get filled immediately by liquid-y jam, it’s ready to can.

If the path fills in with blackberry jam, keep boiling and stirring. Wash the plate, dry completely, and put it back in the freezer. Test after another ten minutes until the path your finger makes stays clear.

Ladle blackberry jam into prepared jars, leaving ¼” headspace. If you are not planning on water bath processing, set aside and let cool at room temperature without moving overnight, then move to the ‘fridge or freezer.

To water bath can, heat a large stockpot of water to boiling. Carefully lower the jars of blackberry jam into the boiling water (make sure the water is at least an inch above the jars). Boil for five minutes, then remove to cool on the counter overnight. Listen for the lid to “pop,” indicating a seal. This might take a full 24 hours. If the lids don’t pop, you could either remove the lid, add a new one, and reprocess, or you can place in the freezer or ‘fridge.

Blackberry jam is good in the ‘fridge for a couple weeks (maybe more, depending on how much sugar you used), and correctly processed for years.

Recipe Notes

You could make a sugar-free blackberry jam with sweet berries and lots of time, too. Keep the lemon juice to brighten up your berry flavor.

For a blackberry jam recipe with pectin, follow the directions on the pectin package for best results.

If you prefer a seedless jam, strain the jam after it thickens and before pouring into jars. This is a bit of an arduous task but results in a silky-smooth jam.

Go even further and add a tablespoon of fresh lavender to the jam and let it cool slightly before straining again and processing as desired.