A guide on blueberry cultivation, planting to harvesting
Blueberry plantings are relatively expensive compared to short term crops because of the higher initial investment, but they will remain productive for an extended duration and can provide an abundance of crop for more than 30 years.
Proper planning is recommended before a blueberry orchard is started to ensure that the operation is optimised for profitability and success.
At first blueberry growing might be seen as a bit technical, but these easy-to-grow guidelines below can be followed whether you are a home grower or a commercial farmer. If more specific details are required.
Blueberries belongs to Vacciniaceae, a sub-family of Ericaceae. They are ericaceous plants, meaning much like Rhododendrons, Azaleas and Camellias, they need to grow in very acidic soil with a ph between 4.2 and 5.5. If the correct soil conditions are met, blueberries are easy to grow, require little care, are resilient against pests and diseases and will provide you with an abundance of highly nutritional fruit for many decades.
Most of the blueberry varieties that we grow and sell to the major nurseries, chain stores and individuals are self-fertile and therefore do not need another blueberry plant for cross pollination. Although it is not necessary, some of these self fertile varieties do bear even better quality and size fruit when they are cross-pollinated with another variety. We can also provide various rabbiteye varieties that are generally higher yielding but do require another variety for cross pollination.
We grow many varieties to cater for specific needs, areas and different fruiting windows. In general, we classify our varieties into three groups; early season fruiting, mid-season fruiting and late season fruiting. With these options, it can be possible to have fresh nutritional blueberries for 6-8 months during the year depending on your area.
Site selection and preparation:
Blueberry plants require superior soil growing media with good drainage and internal aeration as well as good water holding capacity. Ideally, the soil should be sandy loam in texture with an organic percentage of 3% or more. Preferably sites where agricultural lime was not previously worked in which would have artificially raised the ph level and might be too high to economically lower the ph level to around 4.5 (KCl ph).
Elemental sulphur can be used to lower the soil ph, but it takes time for the soil bacteria to break down and adjust the ph which can take 6 -12 months depending on the climate and soil conditions. Composted and untreated pine bark can be worked into the soil to lower the ph level and to add organic matter. Sphagnum peat moss can also be incorporated as this is a great natural product that will lower the soil ph level, helps with aeration and water retention.
Blueberry bushes prefer full sun but they can tolerate partly shade.
Blueberry roots are very shallow and require aeration. The roots are fine, fibrous and do not have root hairs and therefore do not compete well against weeds which must be eliminated before planting. Weed control should begin the year before planting with means of herbicides and/or cultivation. Avoid sites that are water logged, have poor drainage or have a permeable layer close to the surface. Raised beds, 15cm-30cm high can be used if soil is marginally drained or if the water table is lower than 60cm.
Blueberry plants can also be container grown in pots or bags. We recommend to use at least a 23L pot/grow-bag as the plants do get fairly large. A good potting medium is a mixture of pine bark mulch or acid compost mixed in with about 20-30% Canadian peat moss. The plant can then be directly planted into this mixture. A bit (about 15%) of sandy soil can also be used if it has been tested to ensure that the ph level is less than 6.0.
If planted directly into the ground, a hole with the size of 40cm x 40cm x 40cm can be made where the mixture, mentioned above, can be placed into. When transplanting the plant, make sure to plant it at the same depth to ensure that the crown is not covered or the roots exposed. If peat moss is used in the planting medium, make sure to first wet it well, otherwise it will act as a wick and draw the moisture from the plant roots.
As mentioned in the site selection section, blueberry plants can easily be planted in containers, but a fairly large size would be needed in order for the plant to thrive and produce a good crop. If planted directly into the ground, a hole of 40cm x 40cm x 40cm can be made where the planting medium can be placed into.
When transplanting the plant, make sure to plant it at the same depth to ensure that the crown is not covered or the roots exposed. If peat moss is used in the planting medium, make sure to first wet it well otherwise it will act as a wick and draw the moisture from the plant roots.
A thick layer (10-15cm) of pine bark mulch, pine needles or saw dust can be used as a mulch as a protection from extreme heat and cold temperatures. It will also help to retain moisture and to lower the ph level as it breaks down over the years. Avoid placing too rich fertilizers such as manures or chemical fertilizers in the plating hole as they may burn the roots.
Blueberry plants can be planted as close as 60cm apart which will form a thick hedge after a couple of years, but in general most fields are planted using a plant spacing of 0.9m to 1.2m between plants with spacing between rows of 1.8m to 2.8m which would result in a plant density of 3000 to 6200 plants per hectare.
The distances between the rows will depend on which equipment will be used for cultivation, harvesting and pruning. With smaller scale operations hand harvesting is normally used where the row spacing’s are narrower. Most blueberry farmers plant about 6000 plants per Ha, but some who use 25L to 28L pots or grow-bags plant up to 8500 plants per Ha for optimum production.
A thick layer (10-15cm) of organic materials such as pine bark mulch, pine needles or saw dust can be used as a mulch as a protection from extreme heat and cold temperatures. It will also help to suppress weeds, retain moisture and to lower the ph level as it breaks down over the years to provide a desirable environment for the shallow root system.
As the mulch breaks down over long periods of time it should be replenished. Do not use bark or saw dust from redwood or cedar trees.
The amount of water needed per plant or plantation would depend on the soil type, rainfall and climate conditions. Compared to other fruit crops blueberries do not need much water but care must be taken to keep the moisture consistent, but not overwatered. Younger, newly established plants require the most care to make sure that their roots do not dry out or get waterlogged.
During the summer months, when the plant is growing and fruiting, 20mm to 30mm of water is needed per week. This amount is dramatically lowered during the winter season when the plants are in their dormant phase.
Irrigation is usually applied with drip irrigation, but micro sprinklers and overhead irrigation can also be successfully used. Irrigation during late summer and early fall will stimulate fruit bud formation which would increase the yield of the following harvest.
Fertilising your Blueberries
Blueberries are very sensitive to over fertilization and readily soluble fertilizers can cause plant injury and death if applied incorrectly. With these plants a “spoon feeding” approach must be taken where small amounts, more often provided, is best.
Traditionally blueberries do not require as much fertilizer as other crops, but a well balanced fertilization program is necessary for optimum plant growth and crop production.
Start to fertilize in early spring and stop during mid-summer to avoid too much new shoot growth during late summer and early fall which may lead to winter injury on the tender new shoots.
For commercial operations we recommend to have the soil and water tested before adding any nutrients into the soil or water.
Blueberry plants are salt and nitrate sensitive. Nitrates and chlorides should be avoided in fertilizer blends for blueberry plants. It is recommended to use fertilizers that provide nitrogen in the form of ammonia such as, Ammonium Sulphate (21%N), Mono Ammonium Phosphate (MAP) or Urea.
Ammonium Sulphate generally works well as the plant would use the nitrogen in the ammonium form and would also react with the soil to assist in lowering the ph level during long periods of time. Only use 5g (1 teaspoon) Ammonium Sulphate every 3-4 weeks on small, one year old plants and water in well.
Spread the fertilizer along the top of the roots and avoid fertilizing on the crown (stem) of the plant. If the soil ph is below 5.0, Urea nitrogen is preferred as it will not lower the soil ph over time. Potassium Sulphate or Mono-potassium Phosphate (MKP) are suitable sources or potassium.
Alternatively a very slow release, coated fertilizer can be used to provide a wide range of nutrients. Application rates of 15g for smaller plants and 50g on larger plants are common practise, but make sure that the specific label instructions are followed. Blood meal, cottonseed meal and soya meal are very good sources of organic fertilizers.
Avoid using manures as they are normally too alkaline when decomposed, contains salts and rich in nitrate nitrogen which can damage the plants.
Pruning your Blueberries
No heavy pruning is needed during the first 4 years of the plant, but the fine twiggy, low growing vegetative shoots that grow sideways and do not bear fruit, should be pruned out. Remove any dead wood leaving any bright coloured lateral branches.
On older plants, some of the older branches must be pruned during winter or after harvest to promote new growth and assist with air circulation and light penetration. Leave 8-12 healthy, upright canes which are younger than 6 years old as they will produce the best quality fruit.
New suckers will grow from the crown each year. To avoid crowding and to keep your bushes young, keep the two healthiest and strongest looking suckers and prune off others if there are more than two. Pruning is normally done after harvest with the Southern High Bush and during winter with the Northern High Bush and Rabbiteye varieties.
Pests and birds
In Africa we are fortunate that not many natural pests and diseases are found on the blueberry plants and fruit. Blueberries are resilient to many of the common problems associated with other soft fruits.
Other than than minor pressures from insects such as bollworms, aphids, thrips, weevils, beetles, grasshoppers, locust and a few bird species, pests and diseases are not a serious problem.
An integrated pest management programme can be incorporated for crop protection and there are many registered chemical and organic pesticides available. Birds can be a localized issue and bird netting can be used if desired if a great percentage of the fruit is eaten.
Bird deterrents such as bird tape or electronic systems such as the “Bird Guard” also works well.