Blueberries - Vaccinium spp.
Blueberries are members of the Ericaceae or Heath family, genus Vaccinium, subgenus Cyanococcus. The genus is very
diverse, containing 150 to 450 species, mostly found in the tropics at
high elevation, but also in temperate and boreal regions. Most are
shrubs like the blueberries, but again, a diverse range of growth forms
from epiphytes to trees exists.
Three commercially important blueberry species are recognized, along
with two interspecific hybrids:
1. Northern Highbush blueberry (V. corymbosum
L.).
2. Rabbiteye blueberry (V. ashei Reade).
3. Lowbush blueberry (V.
angustifolium Ait., V. myrtilloides Michx., primarily, but other
species such as V. Brittonii and
V. Lamarckii my co-exist).
4. Southern highbush (V. corymbosum
hybrids with V. darrowi, V. ashei, and
other southern Vaccinium species).
5. Half-high highbush (V. corymbosum
x V. angustifolium).
Northern Highbush (right) and rabbiteye (left)
|
Lowbush blueberries in Nova Scotia (courtesy D. Scott NeSmith).
|
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ORIGIN, HISTORY OF CULTIVATION
Cultivated blueberries were domesticated only in the
twentieth century, but probably were collected from the wild for
thousands of years in North America. Prior to 1900, superior wild
bushes were known to be cultivated, supplementing the wild harvested
berries. Today,
75-100 named cultivars exist, and new cultivars are being produced
annually. The present-day industry in the USA is concentrated in the northeastern states. In
the southeastern USA, rabbiteye and southern highbush blueberries have become an important
crop, having been domesticated only in the last 50 years or so. Over
the last two decades, interest in blueberry as a crop is increasing in
other countries and the western states of the US.
World (2004 FAO) - 238,620 MT
or 525 million pounds. Blueberries are produced commercially in 16
countries worldwide on about 120,000 acres.
Top 10 Countries
(% of world production) |
1. USA (56%)
|
6. Romania (1%) |
| 2. Canada (29%) |
7. New Zealand (<1%) |
3. Poland (8%)
|
8. Italy (<1%) |
| 4. Netherlands (2%) |
9. France (<1%) |
5. Lithuania (1%)
|
10. Mexico (<1%) |
United States (2004 USDA) -
124,945 MT or 275 million lbs. The industry value is $295 million, and
prices paid to growers average $1.21/lb for fresh fruit. Processed
fruit receive only 67-95 ¢/lb. Wild-harvested lowbush
blueberries receive $1.20 to
$1.40/lb fresh, but 99% of the crop is processed and valued at 25-40
¢/lb. In 2004, acreage of cultivated blueberries was
44,430, with 30,000 acres of wild-harvested lowbush. Yield average is
5,120 lbs/acre. The leading blueberry states are MI, ME, NJ, OR, NC.
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Plant
Highbush (northern
and southern). Erect, deciduous shrubs, to 12'; 4-7' in
cultivation. Shrubs composed of canes which arise from the crown or
roots; canes have about a 4 year productive life in northern highbush.
Leaves are small (1-2 inch length), ovate or elliptic, with entire
margins and acute tips.
Rabbiteye.
Erect, deciduous shrub to 20' in the wild, 4-10' in cultivation.
Canes arise from the crown or roots like highbush, but have about
a 7 year productive life in rabbiteye. Leaves are similar to highbush.
Lowbush.
Low-growing (<2 ft, usually 8"), creeping, rhizomatous shrubs. The main portion of plant is rhizome or underground stem,
1 to 3" below the surface, which produces upright shoots along its
length. The uprights grow vegetatively for one year, then fruit in
subsequent years. Leaves are smaller than highbush or rabbiteye
(½ inch) and have mildly serrate margins.
Flowers
For all species - White or cream flowers (1-16,
usually 7-10) are borne on short racemes (1-2 inches), on upper portion
of 1-yr-old wood. Flowers are urn-shaped and inverted, on very short
pedicels (nearly sessile), with inferior ovaries.
Pollination
Most northern highbush are self-fruitful, but for
some cultivars, higher fruit set and larger fruit can be produced
through cross pollination. Southern highbush cultivars, in contrast,
are only partially self-fruitful, and are often provided pollinizers in
commercial production. Rabbiteye and Lowbush are highly
self-incompatible, and must have a pollinizer to set fruit. Bumble bees (Bumbus
spp.) and wild bees (e.g., the southeastern blueberry bee Harbropoda laboriosa) pollinate
flowers naturally, whereas honey bees (Apis
mellifera) are reportedly less effective.
Fruit
In all cases, the fruit is an epigynous or "false"
berry. All species
require a high degree of fruit set for a full crop (60-80%) - no
thinning is practiced.
Northern and
Southern Highbush - blue-black color; good to excellent fruit
quality. Shortest period from flowering to maturity of all blueberries
(45-75 days).
Rabbiteye -
blue-black color; good fruit quality, Fruit mature in about 90 days from bloom, so despite
earlier bloom date than Highbush, fruit ripen later.
Lowbush
-black to bright blue color, fair/poor fruit quality compared to other
cultivated types; virtually all commercially grown lowbush blueberries
are processed for muffins and cakes. Intermediate fruit maturation
period of 70-90 days.
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Soils and Climate
Light, acid soils (pH 4.5-5.2) with high organic matter (20-50%) are preferred, unlike most fruit crops.
Blueberries cannot tolerate nitrate nitrogen, and are often fertilized with ammonium sulphate. A large constraint on the distribution of various
blueberry types in the eastern US is winter chilling requirement. The requirements are:
Highbush
800 - 1100 hr
Rabbiteye
350 - 800 hr
Southern Highbush
200 - 700 hr
Lowbush
1000 hr
All
blueberries bloom relatively early, and often experience frost
damage. Open flowers of all types are killed at 28°F.
Propagation - Hardwood and softwood cuttings are the most popular
methods.
Rootstocks
- None
Planting Design,
Training, Pruning
Planting Design: hedgerow
configurations, usually spaced 4 x 9-10 ft ( 1000 bushes/acre), rabbit
eye - 5-8 x 12-14 ft
Hedge height 6-7 ft for
mechanical harvest.
Pruning: highbush - removal of weak wood and older,
unproductive canes
lowbush - burning or mowing
in alternate years to a height of 1-2 inches
HARVEST, POSTHARVEST HANDLING
Maturity
Blue color is the most often used
indicator of maturity. Berries turn from green to pink, and then
gradually to a complete blue color, at which time they are ripe. Ripe
berries will remain attached for several days or weeks, and sugars
continue to accumulate.
Harvest Method
Berries are picked over several times by hand for
fresh sales, and mostly machine harvested for processing. Since berries
ripen over a period of weeks, more than one pass with the harvester may
be necessary. Lowbush blueberries are harvested by hand rakes,
although some mechanical harvesters have been developed.
Postharvest Handling, Storage
Blueberries are fairly perishable, having shelf life
of only 2 weeks when stored at 32 F and 90-95% humidity. Fruit
rots like Botrytis, Alternaria,
Phomopsis, and anthracnose are major storage problems.
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Processed blueberries are used mostly in baked
goods
like muffins, pies, cakes, etc. Juice is a recent innovation, but alone
is unpopular. Blueberry juice is too dark and thick for drinking, so is
diluted 50%, adding sugar and citric acid back to taste. This juice is
mixed with cranberry or other juices (e.g., Ocean Spray products). Per
capita consumption is 0.78 lbs/year.
Dietary value, per 100 g edible portion:
Constituent
|
Blueberry |
Water (%)
|
83-87
|
Calories
|
51-62
|
Protein (%)
|
0.4-0.7
|
| Fat (%) |
0.5
|
Carbohydrate (%)
|
12-15
|
Crude fiber (%)
|
1.5
|
|
% RDA |
| Vitamin A |
2
|
Thiamin, B1
|
4
|
| Riboflavin, B2 |
4
|
Niacin
|
2-3
|
| Vitamin C |
6-31
|
Calcium
|
1-2
|
| Magnesium |
-- |
| Phosphorus |
1-2
|
Iron
|
2-10
|
Sodium
|
<1 |
| Potassium |
1-2
|
* Percent of recommended daily allowance set by FDA, assuming a 154 lb
male adult, 2700 calories per day.
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