Growing cranberries in your backyard is one of the easiest ways to put homegrown food on the holiday table. Cranberries are perennial, and once planted they’ll keep producing crops year after year even with minimal care. Our small 8×8 cranberry bed produces enough to keep our family supplied all winter long, and all it takes is occasional weeding and sand mulch once per year.
I always assumed cranberries were difficult to grow. Don’t they grow in a swamp? Don’t you need to flood the fields? We’ve all seen those ocean spray commercials with a thick layer of cranberries floating on waist deep water.
The truth is, growing cranberries isn’t much different than growing other small fruits like blueberries or raspberries. The berries themselves grow on low growing perennial groundcover. Left to their own devices, cranberry plants send out runners a bit like strawberry plants, and re-root as they go until they cover large areas of soil. Sure, you can flood a field with waist deep water to harvest them…or you can just pick them. Simple as that.
Growing Cranberries from Seed
Cranberry plants grow readily from seed, and a bag of fresh grown cranberries purchased for the holiday season is all you need to get started. Carefully cut open the fresh fruits and pick the tiny seeds out onto a damp paper towel. The seeds are very small, about the size of strawberry seeds, and they’re easy to lose. It doesn’t much matter, as a single one pound bag of cranberries will have hundreds, if not thousands of seeds.
Fold up the damp paper towel around the seeds and place it in a plastic bag in the refrigerator. Don’t seal the bag, a bit of airflow is good for the seeds. Check on it every week or two so that the paper towel doesn’t dry out, but otherwise ignore it for the next 3 months. Cranberry seeds need to cold stratify for around 3 months to sprout. Our winter lasts a full 5-6 months here in zone 4 Vermont, and our cranberry seeds hunkered down in the fridge that whole time.
Once temperatures warm up, bring the seeds out of the fridge and plant them in a rich peat based starting mixture. Cranberries like acidic soils and peat helps to mimic their natural environment. Keep them warm, around 70 degrees and the cranberry seeds should sprout in about 3 weeks, but sometimes it can take much longer. Be patient, and keep the soil moist but not soggy.
Once the plants’ sprout, allow them to grow in pots for their first year. The tiny plants will be fragile, and it’s best to wait until they develop a good root system. Transplant them into a permanent bed in the fall, about a month before the ground freezes over for the winter.
Seed grown cranberry plants will take 3-4 years before fruiting.
How to Grow Cranberry Plants
While cranberries can be grown from seed, these days most people start with potted up nursery cranberry plants. Choose plants that have deep green foliage and ample runners escaping the pot. Plant cranberries in rich sandy soil, ideally with a bit of peat added. Cranberries generally like moist soils with high acid content, and peat helps to acidify the soil and hold moisture.
In an ideal situation, plant cranberries in a bed filled with 2 parts peat and 1 part sand, with clay soil underneath to retain moisture. The extra acidity in the peat helps support mycorrhizal fungus that works with the cranberries to maintain their health, and as an added bonus the acid suppresses weeds at the same time.
If cranberries are planted in the spring, in a few weeks you’ll see the first cranberry flowers.
Cranberries are a groundcover plant, but they spread slowly. Grass competition can choke the young plants, but once they’re firmly established they’ll outcompete most weeds. To help the cranberry plants spread it’s best to mulch them with a covering of sand each fall. The sand mulch helps to bury the side runners and give them a signal to set down new roots.
As cranberry plants set down new roots they’ll colonize new territory and grow in thicker. Eventually, after a few years, they should have completely taken over a bed, assuming they’re initially planted about 18 inches apart.
Here’s one of our cranberry plants fruiting in October here in Vermont. Note the sand mulch all around the plant’s base. Even still, you can see rogue strands of grass growing up through the body of the cranberry plant. It can be tricky to weed in between the delicate runners without damaging the fruit. That’s why sand mulch is helpful because it suppresses grass and encourages cranberry root formation.
How to Harvest Cranberries
Cranberries do float, and it saves work for large commercial operations to just flood the fields and harvest them all in mass. For the rest of us, they’re easily picked by hand. We harvest our homegrown cranberries in mid-October, just before the first hard frosts here in zone 4.
Cranberries store for extended periods naturally, and they’ll make it just fine in a bag in the fridge until the holiday season. That assumes you handle them gently, and pick them over to remove any broken fruits. If you’re saving them for a holiday cranberry sauce, that sauce will improve with a little bit of age. I harvest our backyard cranberries and then can cranberry sauce with cinnamon and spices right away to allow it to meld into a tasty preserve before Thanksgiving.
If you forget to pick the cranberries before it snows, fear not. They’ll still be there in the spring. I know it sounds wierd, but so long as they stay insulated under the snow you can harvest cranberries the following spring once the snow melts out. This handful of cranberries was harvested in early April, just as the snow was melting out. Since I know where they’re growing, I could have harvested cranberries all winter in that spot. That’s just one way our ancestors preserved cranberries in the field before the advent of refrigeration.
Once the snow melts, however, overwintered cranberries won’t keep. Think of them like a bag of cranberries you’ve pulled out of the freezer. Once they thaw they need to be kept in the refrigerator and used within a few days so they don’t spoil. If you’re in a rush, they’ll dehydrate nicely, or you can simply keep them frozen by bagging them up and putting them inside the freezer indoors.