Blueberries are probably the most widely distributed fruit in the world. The blueberry thrives only on organic, acidic soils, doing best at a pH of 4.5 – 5.0. The fruit of at least seven species is harvested on a fairly large scale, including Vaccinium angustifolium, the lowbush blueberry. The highbush blueberry, V. corymbosum, is found throughout the Atlantic Coastal Plain from New England to Georgia, and westward to Lake Michigan. The rabbiteye blueberry, V. ashei, grows mainly in the Southeast.
The lowbush blueberry is gathered in quantities from the wild across the country. The Northern highbush blueberry is the most commonly cultivated type of blueberry in the U.S. A good portion of the production comes from the Northeast and the Pacific Northwest. The rabbiteye blueberry is tolerant of the heat and drought of the South and grows wild.
In order for blueberry production to be successful, they need to be grown in areas that can satisfy the plants’ chilling requirement, known as chilling hours. A chilling hour is an hour below 45º F during winter. This chilling requirement reduces winter injury by keeping the plants dormant. Both blueberry twigs and individual flower buds can be killed or damaged by low temperatures. The temperatures that are critical depend on the degree of dormancy the plants have attained at the time the cold occurs, and to some extent on the variety. Well-hardened northern highbush plants in Michigan can withstand temperatures as low as -22º F without damage. An early hard freeze, before the plants are fully dormant, may cause more damage than much colder temperatures that occur after the plant is fully hardened.
Variety selection is one of the most important decisions a blueberry grower can make. Yield, ripening time, longevity of the planting, ease of harvest and packing and demand for the product are strongly influenced by variety choice.
Vegetatively propagated varieties have been developed for each type of commercial blueberry: northern highbush, southern highbush, rabbiteye, half-high and lowbush. Except for lowbush blueberries, in which the commercial crop is still harvested almost entirely from wild seedling populations, essentially all blueberry production comes from vegetatively propagated improved varieties.
The first northern highbush blueberry varieties were released by the USDA from crosses made in 1912. The breeding of northern highbush varieties began with a group of wild plants, most of which were from New Jersey and New Hampshire. As a result, northern highbush varieties have a high chilling requirement. Low-chill highbush came to be called “southern highbush” because the first varieties were bred for the warmer Southeast.
Blueberry chilling requirement figures usually have been determined under eastern U.S. conditions and should be taken only as a guide. Rabbiteye blueberries require the least winter chill (perhaps 100 – 200 degree hours below 45º F) while some southern highbush cultivars may require more chilling. Northern highbush can require over 600 hours. “Elliot,” a northern highbush, is said to require more than 800 hours.
Although it is convenient to separate northern highbush from southern highbush based on chill requirement, there are other important differences between the groups. Compared to northern varieties, southern highbush tend to continue growing later into autumn and are less winter hardy. Southern highbush varieties tend to flower earlier in the spring. In general, berries of the better southern highbush varieties hold their firmness and flavor better than northern highbush during hot weather. Southern highbush are more likely to be resistant to the diseases of warm areas, such as Phytophthora root rot, Botryosphaeria stem blight and Botryosphaeria stem canker.
Rabbiteye varieties tend to be highly vigorous and sprout canes from the base, as compared to highbush varieties. Although rabbiteye varieties have a low chilling requirement, they have a longer flowering-to-ripening interval than highbush. In the southeastern U.S., the earliest rabbiteye varieties ripen about a month later than the earliest southern highbush varieties grown at the same location. Rabbiteye plants are more drought tolerant than highbush, and more tolerant of soils low in organic matter.
The following is a list of blueberry varieties based on type and chilling requirement. These are only a few of the many that are available. It is essential for growers to find out what varieties have done well in their area and to make a wise selection by knowing as much as possible about each variety.
Northern Highbush Varieties
- Bluecrop. Introduced 1952 by USDA, Beltsville, MD. Bush vigorous, upright, very productive, fruit cluster loose; berry large, very light blue, firm slightly aromatic, medium dessert quality; scar one of the best, resistant to cracking, drops somewhat; early midseason; hardier than most others, drought-resistant. Well-liked for consistent productiveness, hardiness and light blue color. The most planted blueberry variety in the history of the industry.
- Bluejay. Introduced 1978 by Michigan State University. Bush extremely vigorous, upright. Berry size medium, good scar and firmness, berries hold up well on the bush after ripening. Ripens 5-7 days before Bluecrop.
- Blueray. Introduced 1955 by USDA from plots in New Jersey. Bush vigorous, upright, spreading, productive; fruit clusters rather small and tight. Berry very large light blue, firm, aromatic, high dessert quality; scar medium, resistant to cracking. Early midseason. Hardy bush and large high-flavored berries.
- Duke. Introduced 1987 by USDA and Rutgers University. Bush vigorous, upright, consistently productive; self-fruitful; canes numerous, stocky, moderately branched. Flowers late. Berry medium to large, firm, small dry scar, good color and firmness; flavor mild; good shipping quality. Ripens early. Has been the most widely planted blueberry in North America during the past several years. Valued for its earliness, high yields, easy harvest and excellent post-harvest qualities.
Southern Highbush Varieties
- Bladen. Introduced 1994 by North Carolina State University. Bush upright, vigorous, productive. Not fully self-fruitful; resistant to cane canker; has field resistance to stem blight. Chill requirement 800-1,000 hours. Berry medium size, dark blue; good scar, firmness and flavor. Ripens early, about with Reveille.
- Legacy. Introduced 1993 by USDA and Rutgers. Bush vigorous, upright open-growing. Flowers late. Chill requirement 400 hours. Berry medium size, good scar, firmness, flavor; tart when first ripe.
- O’Neal. Introduced 1987 by NCSU. Bush vigorous, open-growing. Chill requirement 400-500 hours. Berry large, dark blue; good scar and firmness. Good flavor, sweet. Early ripening. One of the most successful and widely planted southern highbush varieties.
- Reveille. Introduced 1990 by NCSU. Bush vigorous, upright, productive, self-fruitful. Chill requirement 800-1,000 hours. Berry medium size; light blue; superior firmness, good scar and flavor. Ripens early, with O’Neal and Bladen.
- Ira. Introduced 1997 by NCSU. Bush upright, medium to high vigor, self-fertile in North Carolina, productive. Chill requirement 400 hours. Berry medium to large, color medium blue, good scar, firmness, flavor; aromatic; good storage life.
- Montgomery. Introduced 1997 by NCSU. Bush moderately vigorous, semi-upright, easy to train. Partially self-fertile but needs cross pollination. Consistently productive. Berry medium size. Good scar, color and aromatic flavor. Firmness average, similar to Premier. Resistant to cracking, stemming and tearing, with shelf-life superior to Premier.
- Onslow. Introduced 2001 by NCSU. Bush highly vigorous, very upright, self-fruitful in North Carolina; flowers with Powderblue; ripens late-midseason to late. Berry large, excellent scar and firmness. Resistant to stemming, tearing and cracking. Color medium blue, flavor pleasant and aromatic; stores well.
- Powderblue. Introduced 1978 by NCSU. Plant vigorous and productive. Not fully self-fruitful. Berry medium to large, light blue color, good scar, firmness and flavor. Ripens mid to late-season.
- Premier. Introduced 1978 by NCSU. Plant vigorous and productive; not fully self-fruitful; susceptible to blueberry gall midge. Berry large, scar and flavor good; firmness medium, color dark blue. Ripens early.
Some of the above information was adapted from “The Blueberry” by Norman F. Childers and Paul M. Lyrene.