How To Grow Blueberries From Seed
Blueberries are a powerhouse of nutrition, flavor, and versatility, from culinary uses to landscape applications. To propagate more of the durable, high-yielding shrubs in numbers and with little investment, growing them from seed is a straightforward labor of love. Gardening expert Katherine Rowe explores how to grow blueberries from seed for years of sweet rewards.
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For the ambitious gardener, growing blueberries from seed is an economical way to produce the favorite fruits in numbers. Whether creating a lowbush ground cover or a highbush hedge, the ornamental shrubs bring multi-season appeal in addition to their valuable fruits.
Growing blueberries from seed is a slow process, but the long-lived shrubs bring a high return on the investment of patient tending. Among the highest fruits in antioxidants, blueberries pack the nutrition. They’re also a crop native to North America, with selections from wild (Vaccinium angustifolium) to those cultivated for performance and growing region.
To achieve the benefits of growing blueberries from seed, start by processing fresh berries this summer for starting indoors. The experiment can lead to decades of enjoyment from your own fresh, homegrown berry supply.
Growing Blueberries From Seed
Blueberries usually propagate through softwood cuttings, hardwood cuttings, and the rooting of suckering offshoots (runners). Starting them from seed takes time, with seedlings reaching five to six inches in the first year and one to two feet in the second year. It’s in the second year that the young plants likely begin to bear fruit, with higher yields in subsequent seasons. Aim to cold stratify seeds in the fall or early spring for transplanting the following year.
Blueberry bushes need exposure to cool temperatures to initiate growth, flowering, and fruiting. They rely on a chill period of several weeks between 32 and 45°F (0-7°C). Chill hours regulate the shrub’s growth and signal when it’s time to break dormancy.
Cold Stratification
The seeds, too, need cold stratification to germinate. Many seeds benefit from a cool period to break down internal inhibitors for germination.
Cold stratification for blueberries can take anywhere from 30 to 120 days, depending on the environment and storage time. If seeds have only been dried or berries frozen for about a month, place them in the refrigerator to stratify for 30 days. If there has been longer dry storage or frozen berry storage, refrigerate them for 90 days or as long as 120 days. Experiment with sowing them at intervals for best success.
There are two primary ways to cold stratify the seeds. The first is to place them in a tray of moist, fine sphagnum moss outdoors in the fall. Place them on a two to three-inch layer of moistened moss, and cover them very lightly at ⅛ to ¼ inch. Let them overwinter, and begin watering the media in spring to awaken the seeds. The other method is to place them in a baggie on a damp paper towel or in moistened sand or sphagnum. Keep them in the refrigerator for 90 days prior to sowing.
Processing
If you’ve collected wild or store-bought berries, they’ll need to be separated from the fruit for easy sowing. A kitchen blender offers a simple way to separate them, as does hand mashing with a mortar and pestle. Sow them after processing or store them dry for future use.
- Blend ¾ of a cup of thawed berries in a blender filled ¾ full of water.
- Run it on high for 10-15 seconds and let it settle for five minutes. The berries sink to the bottom, and the pulp floats in the water.
- Slowly pour off some of the pulpy liquid. Add more water, allow for settling, and do another small pour.
- Repeat the cycle of adding water/pouring off until the pulp is gone and the seeds remain. Run the last pour through a towel-lined sieve or colander. Remove the seeds and let them dry on a towel.
By hand:
- Place ¾ cup of thawed berries in a bowl, and mash them to expose the pulp and seeds.
- Add the mixture to a jar with a lid, add water, and shake to separate.
- Use the fill/pour method above to skim all the pulp until the seeds are left. Lay them on a towel to dry for planting or storage.
Plant Selection
Blueberries are rugged and tolerate a wide range of climates and conditions, including winter temperatures as low as -30°F (-34°C). Depending on the variety, they’re hardy in USDA zones 3-10. There are low-bush blueberries, durable as ground covers across growing zones. Northern highbush suits cold climates, while southern highbush and rabbiteye types tolerate heat and require less chill time.
According to your climate, choose one that’s high chill (cold, northern zones) or low chill (warm, southern areas). High chill selections may need 800 to 1000 hours in cool weather, and low chill selections 150 to 800.
Garden Site
In addition to in-ground situations, blueberries grow in containers and raised beds. When choosing your planting site, opt for one with rich, well-draining soil and full sun. They tolerate partial shade, but too much leads to a lack of flowers and berries.
The optimal growing conditions for Vaccinium include:
- Six or more hours of sun
- Highly organic sandy loams
- Acidic soils with a pH between 4.0 and 4.8
- Regular water for evenly moist soils
Blueberries are acid-loving and grow anywhere azaleas and rhododendrons do. Maintain acidity near 4.0 to 4.8 with pine needles, oak leaves, peat moss, and coffee grounds.
Start Blueberry Seeds Indoors
After the necessary cold stratification or with viable, fresh seeds, we’re ready to sow. Fill a tray two to three inches deep with pre-moistened sphagnum peat moss. Opt for finely sifted moss rather than large pieces. Scatter th seeds evenly across the surface, and lightly cover with the moss or ¼ inch of soil. Optionally, cover the entire tray with newspaper.
Ideal soil temperatures for germination are between 60-70°F (16-21°C). Keep the media moist, but not soggy, and place the tray in a warm spot. Blueberry seeds can take up to three months to germinate, but you might see sprouts in several weeks.
Tending Seedlings
Remove the newspaper cover when grassy sprouts emerge. They’ll be tiny, but when they reach a few inches tall, transplant them to three to four-inch pots filled with a peat, sand, potting soil mixture. Take care when separating the tender roots of the young seedlings. Once situated and watered in, place the pots in a sunny, protected spot, and keep the media evenly moist.
After three to four weeks in the pot, apply an organic liquid feed fertilizer at half strength. Plan to house the seedlings in their pots for one year as they develop roots and upper growth.
When they reach six to eight inches, either move them to the garden or into larger containers to continue developing. Use the same potting mix as for seeding or one for acid-loving plants. Let them grow to 12 to 18 inches in the larger pots before transplanting to the garden.
Hardening Off and Transplanting
Tender seedlings benefit from gradual acclimation from indoor growing situations to outside conditions. Before transplanting the young plants, place them in a protected outdoor area for a week to 10 days. Slowly move them to conditions mirroring their new garden location.
Protect them from strong winds, cold nights, and afternoon sun in the process. Hardening off sets the seedlings up for success at transplanting.
Transplant seedlings in the fall during dormancy in mild climates or in early spring in cool climates to allow for chill hours. In areas with late freezes, they’ll benefit from frost cloth protection as tender plantings.
Irrigate and Fertilize
Vaccinium are shallow-rooted and benefit from consistent moisture to flourish. One to two inches of water per week is average during the growing season. Because roots don’t reach deeply for surrounding moisture, the shrubs are sensitive to drought situations. Provide supplemental irrigation during dry spells.
Add a thick layer of mulch in spring and fall. Shredded bark, compost, or leaves work well to insulate roots, regulate soil temperatures, and retain moisture.
Check soil moisture regularly for blueberries in containers, as they dry out more quickly than in-ground plantings. When it’s dry to a couple of inches deep (about two knuckles in), give them water.
Blueberries are sensitive to high-nitrogen fertilizers, especially as seedlings. A balanced fertilizer for acid-loving plants like azalea, holly, rhododendron, and camellia works well at planting to give the seedlings a boost. With organic soils, established shrubs don’t require much, if any, supplemental nutrition. You may opt for an application each spring, or use blood meal, bone meal, and seaweed extract to supply necessary trace minerals and essential elements over time.
Pruning
Like most woody shrubs, blueberries benefit from pruning to retain form and to keep generating fresh growth. Plan to prune in late winter or early spring as the shrubs develop. Young plants only need shaping and thinning to improve air circulation and form as they grow. Remove dead, diseased, or crossing branches any time they crop up. In the first year, deadhead spent flowers to encourage energy to the roots and upper growth.
Established shrubs benefit from the removal of aged canes. Blueberries reach mature size and production at about seven years old. During winter dormancy and after several years of growth, remove old canes that are larger than one inch thick. Removing one out of three mature canes, too, promotes new stems for increased berry production.
