Blueberry growing in South Africa
MPG Smallfruit publication: 1.1, 2003. For more publications, visit WWW.ORCHMAN.COM/MPG
Introduction
The Blueberry belongs to Vacciniaceae, a subfamily of Ericaceae. There are 3 commercial types of blueberry, namely the Highbush,
the
Lowbush and the Rabbiteye blueberry.  The Highbush blueberry has been developed primarily from 2 species, V. corymbosum
and
V. australe. These plants are naturally distributed in sunny, acidic, swampy areas along the eastern coast of North America from
Nova Scotia and southern Quebec west to Wisconsin, and south to northern Florida.
The Lowbush blueberry includes V. myrtilloides Michaux, which ranges from Vancouver island east to Labrador and south to New
York, Indiana and Pennsylvania. The Rabbiteye blueberry (
V. ashei Reade) ranges throughout most of northern Florida, southern
Alabama and Georgia.
The Rabbiteye blueberry (V. ashei Reade) is extremely heterozygous. The plant is generally vigorous, growing to a height of 3 metres
or more. Berries vary in colour from glossy black to light blue, small to medium large in size (15mm). The name Rabbiteye comes
from the observation that the blossom ends of wild
V. ashei blueberries (large shallow calyx) resemble the conformation of the eye
of the common wild rabbit, a pink spot resembling a rabbit’s eye forms on the wild berry when it begins to ripen and takes its dark
colour.
In general, the Rabbiteye blueberry plant is classified as erect, spreading and very vigorous. Vigour is generally thought of as stem
length or plant density, but should consider plant vitality, too. This species is often considered by plant breeders to offer the greatest
possibilities for improvement because of its tolerance to a wide range of soil pH and high temperatures, its inherent drought
resistance and its low chilling requirement.
Commercial blueberry cultivation in the southern and western cape of South Africa is primarily concerned with the Rabbiteye
blueberry and, more recently, the Southern highbush blueberry. This is due to the dormancy chilling requirements for the Northern
highbush and the Lowbush blueberries being too high for these areas (in excess of 700 hours below 7.2oC). Northern Highbush
blueberries are currently undergoing testing in the Orange Freestate and colder, higher altitude locations of the Western Cape in
South Africa.
Propagation
Blueberries are usually propagated from softwood or hardwood cuttings selected from healthy, disease-free mother plants.
Cuttings are placed in a propagation bed in a growing media that holds moisture well, but allows adequate aeration. A peat / fine
pine bark blend or sawdust has proven ideal. Water is delivered by means of an intermittent misting system. The misting system
should apply water for 10 to 30 second periods each 15 to 30 minutes to ensure that the cuttings remain moist.
Certain commercial nurseries may propagate blueberry plants by means of Tissue culture. The shoot tips are induced to produce
multiple shoots in agar media supplied with modified standard culturing solutions. After subculturing, the shoots are cut off and
placed into a peat-perlite rooting mixture under mist, where they root readily.
Establishment and Layout
The blueberry is an acid-loving plant – it requires a low pH soil or growing media (4.2 – 5.0 KCl pH) that is relatively low in Calcium
and Phosphorous, drains easily and has a high percentage (>2.0 %) of organic material present. Due to the fact that the root
system is shallow, fibrous and does not have root hairs present, the plant is a poor competitor for nutrients against weeds. A pine
bark mulch on the row or ridge surface of approximately 5 to 10 cm in depth assists in maintaining the moisture for the shallow
feeder roots, which are often found only a few millimeters below the soil surface. As the mulch breaks down, the roots will grow into
it.
Blueberry plants are usually established as an orchard or field. The plant spacing is commonly 1 to 1.5 metres between plants in
the row by 2.5 to 3 metres between rows. This results in a plant density of between 2666 and 3333 plants per hectare. In shallow
soils or fields that have a relatively shallow water table (< 300mm below the surface), it is preferred to ridge the rows in order to
increase the depth of soil for root development above the water table or clay layer that may be present in a lower horizon.
Figure 1: A cross-section of a ridged blueberry field layout
In trials, it has been found that the plant has a preference for pine bark as a mulch or organic material addition in the soil profile.
Blueberries can be established in pine bark beds or plant pots. The planting density is increased drastically as compared to the
conventional ‘orchard’ layout. A typical spacing for pine bark beds is 900mm between plants within the row by 1.5 metres between
the rows. Although production per plant in such a system is lower, the production per hectare is higher than the ‘orchard’ layout.
The harvest period will depend on environmental factors (climate etc.) and cultivar selections. It is preferred to plant at least three
cultivars in each field. This is not required for Southern Highbush cultivars but it is vital for Rabbiteye cultivars. The Rabbiteye
blueberry is dependent on the presence of compatible companion cultivars for cross-pollination. The companion plants can
either be planted within the same row as the primary cultivar or planted in separate rows. For ease of harvesting, separate rows
have proven more popular on blueberry farms in South Africa to date.
A          A          A          A          A                                   A          B          A          A          A
B          B          B          B          B                                  A          A          B          A          A
A          A          A          A          A                                   A          A          A          B          A
C         C          C         C          C                                  C          A          A          A          B
         Block 1                                                                                  Block 2
Row direction
Figure 2: Cross-pollination considerations in orchard design (3 cultivars: A, B & C)
When the plants are set into the field, it is important to break up the root-ball or make several vertical slashes with a knife. In
transplanting the blueberry plants from the bags into the field, care should be taken to keep the roots from drying out. All flower buds
should be removed from new plants. Newly set plants should not be allowed to flower and fruit in the first year unless the plants
have sufficient growth and leaf numbers to support fruit development.
Blueberry plants should be planted in either late autumn or in early spring. Autumn planting allows the plant more time to establish
roots before the spring growth begins. The plants should be set at the same depth as they grew in the nursery. The shoulder of the
root-ball should not be exposed because this will cause a wicking effect and dry out the root-ball. If the plants are planted too deep,
covering the crown, the plants will seem to be stunted, not showing any growth for a prolonged period.  Do not apply fertilizer in the
planting hole at the time of planting.  Another planting system is to dig individual holes of about 50cm by 50cm in size, and fill these
holes with a mixture of soil and peat moss, and set the plants in the same way as stated previously.
Irrigation
Newly established plants have the most critical water needs, and can be damaged by either over-watering or under-watering. Short
periods (1 to 3 weeks) without rain can stress blueberry plants severely. Irrigation during such periods is required for optimum plant
performance. Irrigation of producing blueberry plants during dry periods before harvest results in larger berries and higher yields.
Irrigation in February and March will stimulate growth and fruit bud formation, thus increasing the potential yield for the following
blueberry season.
A rapid decrease in soil moisture during dry periods increases the concentration of fertilizer nutrients in the soil solution, which may
damage the roots of the blueberry plant. The water requirements of the blueberry plant increases as the plant increases in age and
size, but varies according to soil type, organic matter, and natural climatic conditions.
The irrigation system for blueberries should be suited to the requirement of the plant. It should be able to apply relatively small
amount of water to a wide surface of the soil on a frequent basis. A micro-sprinkler system proves ideal in spreading the water
across the area of the root system. It also aids in ‘watering in’ any fertilizers that may be applied to the soil surface around the plant.
Drip irrigation systems have proven to be problematic in providing sufficient water to the shallow root zone as the soil / organic
material blend is generally too loose and ‘airy’ for the water to spread laterally. Most of the water travels down to the lower soil layers.
In periods when the plant is in need of larger amounts of water, this may prove fatal to the plant, due to the roots drying out and dying.
Many different irrigation systems are in place in commercial blueberry plantings around the globe - central pivot, overhead, drip,
pulse and micro-sprinkler. It is advisable to contract a professional irrigation organization to design and install the irrigation system
most suitable.
Plant nutrition
Although blueberry plants do not, traditionally, require as much fertilizer as most other crops, it is vital to follow a balanced nutritional
program. The blueberry plant is salt sensitive and nitrate sensitive  the correct placement and amounts of fertilizer applied should be
closely monitored. Ensure that no fertilizer is applied directly against the crown of the plant  rather a hollow ‘doughnut’ shape around
the plant, avoiding possible crown damage and ensuring coverage of the whole root area.
Nitrates and chlorides should be avoided in fertilizer blends for blueberry plants. Preferably, Ammonium sulphate, Mono Ammonium
Phosphate (MAP) or Urea should be used as a nitrogen source. Potassium sulphate or Mono Potassium Phosphate (MKP) are
suitable sources or potassium.
Granular or dry fertilizer applications can be applied in just a few applications to reach the target amount for the season. Fertilizer
applications of 30 (younger plants) to 50 grams (older plants) are common practice. Fertigation is a ‘spoon-feeding approach, where
smaller amounts of fertilizer are applied by means of an injector through the irrigation system. Fertilizer can be injected once or twice
a week in this way.
Rabbiteye blueberries require significantly less fertilizer than the Southern and Northern highbush types. A micronutrient blend
should be applied as a foliar spray or through fertigation on a regular basis throughout the growing season. Leaf samples taken on
a regular basis will show if elemental levels are optimum or not within the plant.
Harvesting and Packing
The blueberries will ripen over a period of usually 4 to 6 weeks from the first blue fruit to the last for each cultivar. For shipment of
highly perishable small fruits to fresh markets, consider hand harvesting, grading, and packing into consumer packages, all in one
operation, in the field The harvesting of export blueberry fruit is by hand, thus highly labour intensive. The availability of an adequate
and dependable supply of hand pickers at harvest time is a continuous problem for blueberry growers.
The fruit is picked directly into 125 or 150 gram clamshell punnets, in which the fruit will be sold to the end consumer. The picker is
responsible for size and quality grading. This drastically reduces the amount of handling which the fruit undergoes, and allows the
waxy bloom to remain on the fruit. The punnets are then transported to the refrigeration facility, and reduced to a temperature of 2.0 to
2.2oC, within as short a time period as possible. Thereafter, the punnets are checked and weighed again, as a form of quality
control. This quality control occurs in a refrigerated room, which does not exceed 8oC, alongside the cold room, therefore, a
double-chamber cold room is ideal. The fruit does not leave the refrigerated area until it is packed and sealed into foam export
boxes. From there, it is transported to the nearest airport, or shipped by road, to an international airport, from which it is flown to
overseas markets.
Mechanical harvesting is, as yet, not used in South African blueberry growing. Berries that are mechanically harvested have been of a
lower quality than those that are hand harvested, and traditionally sold only on the processing market. New developments in
mechanical harvesting have resulted in less damage to fruit and a ‘softer’ process. The introduction of blueberry colour sorter
machines has proven successful in the USA.
Pruning
A light pruning may be conducted when planting the blueberry plants in the orchard. The thin, twiggy growth and any sickly or
diseased wood is removed, leaving only healthy, stronger canes. Pruning in subsequent years is based on principles of ensuring a
balance of 8 to 12 canes from young to mature, sufficient light penetration and distribution throughout the plant, leaving no limbs that
may hang onto the ground surface once bearing fruit (skirting the bush) and removal of any old fruiting or dead and diseased wood.
Branches that are removed during pruning should be hauled out of the orchard and destroyed. Blueberry plant pruning is usually
conducted directly after harvest for early season Southern highbush cultivars and during winter for Northern highbush and Rabbiteye
cultivars. The early season Southern highbush cultivars enter a vegetative growth flush within the weeks directly after harvest is
complete. By pruning the plant directly after harvest, stronger, healthier vegetative growth is encouraged as all weak and old fruiting
wood has been removed from the plant.
Cultivar selection
Cultivar selections will determine to a large extent the ripening period and, in turn, the ability to reach targeted market windows
(timeframes). Not all blueberry cultivars available in South Africa are listed.
Rabbiteye cultivars:
Beckyblue
Released by University of Florida in 1978
Chilling requirement is 300 – 400 hours (below 7.2oC)
Blooms early
Harvests late November / early  December
Fruit has reasonable colour, size and firmness
Suggested pollinator: Climax
Aliceblue
Released by University of Florida in 1978
Chilling requirement is 300 – 400 hours
Blooms early
Harvests late November / early December
Bush is upright and vigorous
Cross-incompatible with Beckyblue
Suggested pollinator: Climax
Premier
Released by North Carolina in 1978
Chilling requirement is 550 hours
Good size fruit that is firm, has good colour and flavour
Plant is upright and vigorous in growth habit
Grows better than other rabbiteye cultivars on soils that are marginally high in pH
Suggested pollinator: Climax
Climax
Released by Georgia in 1974
Chilling requirement is 400 – 450 hours
Harvest in December
Fruit is firm
Suggested pollinator: Premier
Does not produce many canes from ground level – do not remove too many canes during renewal pruning.
Brightwell
Released by Georgia
Chilling requirement is 350 – 400 hours
Reliable producer
Ripens December – early January
Plants are vigorous and upright
Berries are medium in size, have small stem scars, good flavour and colour
Subject to overcropping
Partially self-fertile
Suggested pollinators: Powderblue or Premier
Choice
Released by University of Florida in 1985
Chilling requirement of 550 hours
Ripens approximately late December to late January
Fruit is medium sized with good flavour
Suggested pollinators: Brightwell and Powderblue
Tifblue
Released by Georgia in 1955
Chilling requirement is 600 – 800 hours
Ripens December – early February
Medium fruit size
Fruit cracks during wet weather
Plants are vigorous and upright
Suggested pollinators: Brightwell, Briteblue and Powderblue
Delite
Released by Georgia in 1969
Chilling requirement of 500 hours
Ripens late December – January
Fruit is medium – large in size, reddish colour, sweet flavour
Not suitable for commercial production – ideal for home garden.
Centurion
Released by North Carolina in 1978
Chilling requirement of 550 – 650 hours
Blooms late and is partially self-fertile
Harvest late December to early February
Fruit is medium in size
Young plants may develop one sided root system and fall over in high winds
Southern highbush cultivars:
O'Neal
Released by North Carolina in 1987
Chilling requirement is 400 – 500 hours
Harvest late October – mid November
Blooms over an extended period of time
Large, medium-blue fruit that is firm
Semi-upright growth habit
Sharpblue
Released by University of Florida
Chilling requirement is 200 – 300 hours
Ripens in November
Leaf diseases can be a serious problem
Plants are moderately productive
Misty
Released by University of Florida in 1989
Chilling requirement is approximately 200 hours
Fruit ripens early to mid November
Plant is vigorous and upright with dark green foliage
Highly susceptible to stem blight
Tends to leaf poorly and fruit heavily
Georgiagem
Released by Georgia in 1986
Chilling requirement of approximately 350 hours
Ripens mid to late November
Fruit is medium in size
Production is low to medium
Northern highbush cultivars:
The following cultivars are currently under trial in South Africa (no production info available as yet.
Earliblue
Duke
Spartan
Patriot
Bluecrop
Elliot
Pest Management
Crop protection of the commercial blueberry orchard is ideally suited to an I.P.M. (Integrated Pest Management) system in South
Africa. Many natural pests and diseases of the blueberry plant and fruit are not yet present in South Africa, thus making crop
protection easier and possibly even less costly than traditional blueberry growing areas. Certain fruit pests in South Africa have
become commercially important in blueberry growing, namely, American Bollworm (Helicoverpa armigera) and certain bird species.
Minor pests on blueberry plants may include, but are not limited to: aphids, australian bugs, beetles, loopers, grasshoppers and
locusts.
As commercial blueberry growing is still a relatively small industry in South Africa, pesticides have not yet been registered for use on
blueberry plants. Due to the ecology and differences between specific orchard sites, it is ideal to implement a program such as the
Integrated Pest Management Program, monitoring pest and predator populations, and becoming intimately acquainted with the
specific site. After a few years of such monitoring, pest forecasting, scenarios and specific problems can be addressed before they
actually occur.
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M. Greeff