Blueberry Cultivation in the Home Garden
Blueberries are a popular fruit for a lot of good reasons. They have a unique flavor, small edible seeds, can be eaten fresh, and in jellies, jams, pastries, pies and juice. They are low-calorie with no sodium or cholesterol and are a source of fiber. The fiber source, pectin, has been shown to lower blood pressure. They contain ellagic acid which has been shown to inhibit chemically-induced cancer. And various sources indicate that blueberries help reduce the effects of urinary tract infections and glaucoma while improving memory. No wonder they are called a miracle food!
From a gardening standpoint, they are a woody perennial shrub that produces an annual crop of ¼” to ¾” berries. They are a member of the Ericaceae family, related to azaleas and rhododendrons. They are found naturally in well-drained, nutritionally poor, organic soils. Well- managed plants can produce for about 20 years. Major commercial production takes place where such soils are prevalent, including southern New Jersey, southwest Michigan and the Carolina coastal plains. They can be grown in other areas with appropriate site preparation, cultivar selection and ongoing site and cultural management.
Site Selection and Preparation
The best sites are in full sun (at least 6 hours per day), on gentle slopes where cool air and surface water both drain well. Flowers will tolerate mild frosts, but can be damaged by hard frosts and plants should not be located in low lying areas where cold air settles. Plant size varies somewhat with the cultivar, but 5-foot spacing between plants is typical. They can be arranged as a dense hedge, foundation planting or integrated with ornamentals. While many cultivars are self-pollinating, planting at least two cultivars together is recommended since cross pollination produces larger berries, higher yields and earlier ripening. Because most varieties flower at about the same time, careful selection can provide the benefits of cross pollination while extending the harvest season.
Ideal soils are silt loams to sandy texture with 2-3% organic matter. Plants are intolerant of waterlogged soils. Surface and internal drainage are critical to avoid root rot. Raised beds are often employed to improve drainage. Adding composted organic material is recommended to aid both water infiltration and drainage.
Blueberry bushes require a soil pH of 4.5 to 5.2, quite acidic. Addition of agricultural sulphur is the recommended amendment for soils above this pH range. Best to have soil tested and begin amendments in the year prior to planting. Regular testing and continued amending is recommended where soils aren’t naturally in the right pH range as they tend to revert to their natural pH level.
There are several species of blueberry — the lowbush (Vaccinium angustifolium); the highbush (Vaccinium corymbosum; and the rabbiteye (Vaccinium ashei). There are three types recommended for Central Virginia:
- Northern highbush
- Southern highbush
Best choices are influenced by “chilling hours” — the number of hours per year that are in the 35-45 ºF. range needed to satisfy plant dormancy requirements. Northern highbush is best in northern Virginia and the mountain region. Southern highbush and rabbiteye are most appropriate in the central Piedmont, east and south, hardiness zone 7a and higher.
Southern highbush and rabbiteye varieties are hybrids of the northern highbush and are more soil-adaptable and heat-tolerant.
- Early blooming: Alapaha, Climax, Premier, Titan, Vernon
- Mid: Brightwell, Powderblue, Tifblue
- Late: Centurion, Ochlakonee
- Southern highbush:
- Early: Suziblue, Palmetto, O’Neal
- Mid: Camellia, Jubilee, Magnolia
- Northern highbush
- Early: Duke, Earliblue, Patriot, Spartan
- Mid: Bluecrop, Blueray, Legacy
- Late: Elliott, Jersey
Note that the early bloomers are most susceptible to frost damage.
Whichever variety is selected, look for vigorous two year old plants about 15 inches high. Keep bare roots or root balls moist if not planted immediately.
Plant bare root plants in February-March as soon as soil is workable. Container plants are best planted in the September to November period to allow root development over winter. Holes should be twice the size of the root ball. Mix organic matter with prepared soil. Water well before and after planting.
A 3” thick mulch, preferably of pine straw, pine bark or sawdust is recommended to assist in pH management, to maintain moisture, and to control weeds. Sulfur can be added to the mulch surface for further acidification as needed. If voles are a problem, a thinner mulch layer is warranted. Plants require 1-2” of water per week. Blueberry plants are relatively shallow rooted, spreading to only 1 ½-2 feet below the surface.
Best not to allow new plantings to bear fruit until they reach about 30” in height. Remove buds when planting to allow stronger shoot growth and to increase future yields.
Pruning blueberry bushes is very important to maintain productivity. During the first three years, remove low spreading canes, dead and broken branches. After maturity, regular pruning between leaf fall and spring growth is recommended. Cut out old, dead wood. Keep the 3 best one-year-old canes. Prune out about 1 of 6 of the oldest canes, as close to ground level as practical. The goal is to end up with 10-15 total canes, 2 to 3 each at 1,2,3,4 and 5 years.
Birds are probably the major pest risk. Covering the bushes with fine mesh netting or light fabric protects against all but ground entry. Suspending aluminum pie tins above the plants so they twist and ding in the breeze can also be effective.
Be sure to pick ripe berries promptly to avoid drosophila infestations. Note though that berries don’t reach full ripeness for 5-7 days after turning blue. Harvest timing is critical.
Healthy blueberry bushes generate thousands of buds, each with a cluster of 16 flowers, each flower a potential berry. Each berry has many seeds, nearly all of which must be individually fertilized for a healthy, normal sized berry to develop, so active pollination is essential. Blueberry pollen is sticky, but relatively heavy and not likely to reach the stigma without insect intervention. Native bees, including bumble and solitary bees are potential pollinators. Commercial growers often bring in honey bees to augment natives. The insects are attracted by scent and sweet nectar in at the base of the stigma. Nectar and pollen are both food sources. Not all flowers in a cluster open at the same time, but when a flower opens, the pollen and stigma are ready for transfer to take place. Pollination must happen within a few days for a berry to form.
It Takes a Commitment
Successfully growing blueberries, like most good things in life, requires a commitment. From picking the right varieties to managing soil pH and drainage to pruning to pest management. But there has been a lot of work done to provide cultivars that will succeed in our environment and helping us understand the important aspects of caring for them to best assure good berry production. For gardeners willing to take the plunge, the reward can be 20 years of enjoyment of a tasty, healthy, recently anointed superfood.