Last winter, Gen opened the chest freezer and found something like three and a half pounds of blackberries from the previous season — zip-locked in portions, labeled by date in her handwriting, waiting patiently for their moment. We'd frozen them at peak ripeness in July, flat on sheet pans first so they wouldn't clump, then transferred to bags. Perfect condition. The question was what to do with all of them.
Gen had made jam before, but never preserves with our own berries. She pulled out her grandmother's handwritten recipe card — already splattered with decades of use — and adapted it for blackberries. The first batch came out of the canning pot looking nearly purple-black in the jar, and when she cracked one open that evening to test on a biscuit, the family's reaction made it clear we had something worth writing down and sharing.
This is that recipe. It's simple, it uses no commercial pectin, and the lemon isn't just flavoring — it provides the acidity that helps the preserves set and brightens the berry flavor so the finished product tastes fresh even after months on a shelf. Three ingredients plus lemon zest. That's it.
Blackberry Lemon Preserves
Gen Steward's recipe · Steward Farms, Marietta, Georgia
Ingredients
- 4 cups fresh (or thawed frozen) Steward Farms blackberries
- 2 cups granulated sugar
- 2 tablespoons fresh lemon juice
- 1 teaspoon lemon zest
Instructions
- Place two small ceramic plates in the freezer — you'll need these for the set test later. Wash and sterilize four half-pint canning jars and lids by running them through a hot dishwasher cycle or simmering in boiling water for 10 minutes. Keep warm until ready to fill.
- Mash the blackberries in a large, heavy-bottomed pot or Dutch oven using a potato masher. Leave it a bit chunky if you like texture in your preserves, or mash more thoroughly for a smoother result. If you prefer fewer seeds, press the mashed berries through a fine mesh strainer — though we leave most seeds in because they carry flavor.
- Add the sugar, lemon juice, and lemon zest to the pot. Stir well to combine, making sure the sugar is evenly distributed through the berry pulp.
- Place the pot over medium-high heat and bring the mixture to a full rolling boil, stirring constantly with a wooden spoon or silicone spatula. Don't walk away — the sugar can scorch on the bottom in seconds if you stop stirring.
- Once boiling, reduce the heat slightly to maintain a vigorous but controlled simmer. Use a large spoon to skim any pink foam that rises to the surface — this foam won't affect flavor but will cloud your finished preserves if left in.
- Cook for 20–25 minutes, stirring frequently. As the preserves thicken, stir more continuously to prevent sticking. The color will deepen from bright red to a dark, rich purple-black and the mixture will coat the back of your spoon.
- Test the set: remove one of your frozen plates from the freezer and drop a small spoonful of the hot preserve onto it. Wait 30 seconds, then push the dollop with your fingertip. If it wrinkles and holds its shape, the preserves are set. If it runs back into itself, cook for another 3–5 minutes and test again.
- Remove from heat. Ladle the hot preserves into your sterilized jars, leaving 1/4 inch of headspace. Wipe the rims clean with a damp cloth, apply the lids and bands fingertip-tight, then process in a boiling water bath for 10 minutes. Remove and let cool on a towel for 12–24 hours. You'll hear the satisfying pop of the lids sealing as they cool.
Tips for Getting It Right
- How to tell when it's set: The cold plate test is more reliable than cooking time alone. Every batch of berries has slightly different sugar content, so the timing varies. Trust the wrinkle test over the clock.
- Frozen vs. fresh berries: Frozen berries work beautifully and often produce a more consistent set because freezing breaks down the cell walls slightly, releasing more natural pectin. Thaw completely and drain any excess liquid before measuring.
- Storage: Properly sealed jars keep up to 1 year in a cool, dark pantry. Once opened, refrigerate and use within 3 weeks.
- Adding vanilla: A half teaspoon of pure vanilla extract stirred in just before ladling into jars adds a warm note that works beautifully with the blackberry and lemon. Optional, but worth trying.
- No pectin needed: Blackberries are naturally high in pectin, especially when slightly underripe berries are included in the batch. Combined with lemon juice — itself a pectin booster — this recipe sets reliably without commercial pectin.
How to Use It
The obvious answer is on a warm biscuit, and yes, that's correct — do that first. But these preserves are versatile enough to go far beyond breakfast.
The glaze application is underrated. Brush the preserves over a bone-in chicken thigh in the last ten minutes of oven roasting, and the sugars caramelize against the heat while the blackberry and lemon brighten the meat. It sounds unusual but it's become a regular dinner at our house.
If you want to make this recipe with fresh-picked berries from the farm, follow us on Facebook at @stewardfarmsmarietta — we post when berries are available, and they sell quickly. Peak season runs from mid-June through August. Check our 2026 Harvest Calendar to know when to expect the best of the season.
