How to Grow Blueberries
Blueberry is a deciduous shrub that, depending on the variety, can grow up to several feet in height.
In wild, blueberries are widespread in pine, spruce and beech forests. It blooms in May and June and ripens from June to August. The fruit is a round berry, with diameter of 5-10 mm, dark blue and sour-sweet taste.
Fruits contain organic acids, vitamins, minerals, tannins etc. Blueberry fruits have numerous health benefits and their regular consumption leads to improved health and overall well-being.
Leaves in autumn get vivid red color, making blueberry bushes very decorative in any home garden.
Blueberry vs. Bilberry
Bilberry is any of several Eurasian species of low-growing shrubs bearing edible, nearly black berries. The species most often referred to is Vaccinium Myrtillus, but there are several other closely related species. Bilberries are distinct from blueberries, but closely related to them. Most common fruits sold as blueberries are native to North America. Commercially cultivated high-bush blueberries were not introduced into Europe until the 1930s. Anyway, regardless if you are in Europe, Asia, America etc. choose variety and species that is successfully grown locally.
Common Blueberry Species
Besides wild blueberry (also known as low-bush blueberry), there are three main types of cultivated blueberries:
- Vaccinium Angustifolium or Canadian blueberry – low-bush type of blueberries, with the of height 15-45 cm (6 – 18 inches),
- Vaccinium Virgatum - Rabbit-Eye Blueberry or Southern Black Blueberry - can grow 1-2m high, but it is self-infertile and one must grow two or more varieties to pollinate each other.
- Vaccinium Corymbosum or The Northern Highbush Blueberry – high-bush type of blueberries, with average height of 1.5 m to 3 m (5-10 feet).
Low-bush blueberry varieties grow in Canada and the northern areas of the United States, because they prefer colder conditions. High-bush varieties of blueberries prefer a more moderate climate, and are therefore suitable for growing in temperate areas. Anyway, before purchasing blueberry plants, especially if you do it on-line, be sure to check what blueberry varieties grow successfully in your area. Blueberries are not very picky plants, but when grown in conditions they like, they bear great looking and great tasting fruits.
Temperature for Growing Blueberries
Blueberry is very resilient plant and can withstand temperatures from -20 ° C to -25 °C (-5 °F to -13°F) without any damage. If the plant is covered with snow and the roots are protected with some sort of winter cover (thick mulch, for example), blueberries can withstand much lower temperatures.
Watering of the Blueberry Plants
During the growing season, blueberry plants require a lot of moisture and in summer, when temperatures are high, the blueberries must be irrigated. Blueberry plant has a shallow root system and it is very sensitive to the lack of moisture. Without enough water, serious problems can occur, such as dwarf growth, lower yields and in the worst case even entire bushes can die. On the other hand, blueberries don't like soggy soil.
Proper Soil for Growing Blueberries
Blueberries are acidophilus plants (they like acidic soils) with modest requirements for mineral nutrients. They thrive best on positions rich in humus, which are well aerated and very acidic. Blueberries like any acidic soil with pH between 4 and 5.2, but they will grow anywhere between pH 3.5 and 6.5. On lime and similar soils, it will grow successfully, only if acidic humus is added in abundance.
Anyway, before planting your blueberries, be sure to check soil in your garden using home kits – they can be purchased on-line and they are really easy to use (read manuals!). Also, be sure to check several samples, even from various depths.
Selecting a Position for Planting Blueberries
Blueberries prefer warm (warm, not hot!) and sunny positions – this highly depends on your location and chosen varieties. The best positions are gentle slopes with constant air circulation. Blueberries prefer higher humus content (5%) in soil, require constant and adequate moisture. Soggy soil with high groundwater should be avoided. Also, avoid so-called 'frost areas' (depressions where colder air in winter can descend and where temperature can be few degrees lower within several meters!!!), heavy, wet and clay grounds. With such specific requirements, growing blueberries in home garden can be a real challenge.
Blueberries are planted in autumn and winter in locations exposed to the sun. Different varieties of blueberries successfully grow in different climates and in different weather conditions, but generally they thrive in temperate and colder conditions and at medium and high altitudes. It is important to note that blueberries can't endure extreme heat (again, there is huge difference between warm and hot conditions, especially in temperate regions). High temperatures, like 40°C (100°F) or more, combined with direct sun exposure, can:
- cause harmful drying of the roots,
- affect the quality of the fruits,
- can completely destroy the blueberry shrubs.
Selection of species and varieties before planting is very important, because one must choose plants that are adapt to local climate.
Before planting, the soil should be prepared up to a depth of 20 cm (8 inches). If the soil is too moist and/or soggy, blueberries can be grown in mounds or in raised beds 15 - 30 cm (8 – 12 inches) high and 120 cm (4 feet) wide.
Young blueberries are planted in separate holes. It is good practice to add some fertilizer and humus before planting, just be sure that they don't contain calcium or lime (again, proper pH is so important!). That is one of the reasons why blueberries planted along walls and fences don't grow very well (some even die) - lime present in walls and concrete fences enters the ground and influence pH of the soil.
Positions with a pH of 5 to 6 are not acid enough for normal growth and development of the blueberries. If that is the case, than it is recommended increase acidity of soil with application of acidic nitrogen fertilizer (ammonium sulfate) or sulfur (granules, powder). Also, for that purpose, it is possible to add iron or magnesium sulfate. Again, use test kits and calculator to find right amounts of required compounds one should add to the soil. If you are not good with numbers and chemistry, ask local professional (usually found in any larger garden center) to help you – great investment in the long run!
In home gardens, it is best to plant blueberries in mounds or raised beds, because in such habitat regulation of ground water and proper water-air characteristics of the soil are achieved more easily, which helps avoiding incurable disease of root system, healthier and stronger plants and in the end, higher yields of great tasting fruits.
Raised beds are easy to cover with wood sawdust (especially from pine, spruce and beech) that in the long-term reduces the pH, reduces or prevents the growth of weeds and during the summer heat prevents moisture loss. It is good practice to add 10 cm of sawdust every year under shrubs.
Compared with other types of fruits commonly found in home gardens, blueberry root system is shallow, densely intertwined, very compacted and develops into a relatively small area. Most of the blueberry root system grows up to the depth of 35-40 cm (14 – 16 inches).
Planting and Maintaining of Blueberry Plants
Blueberry propagation is done by underground shoots (from the roots). Before planting, any excess soil in which plants were located in the nursery, are removed. Young plants are usually planted in October and November – this of course depends on variety and location.
Before planting, roots are kept in water for few hours. Standard spacing for high-bush blueberry plants is 120 cm (4 feet) in a row and 3 m between rows – in home garden spacing in single rows can be 90-100 cm (3 feet). Blueberries are grown mainly in the form of bushes and hedges. At higher altitudes it is recommended to plant rows in north-south direction for optimum amount of light. At lower altitudes, on warm and sunny locations, priority is given to east-west direction to reduce excessive heat and drying out of the soil.
Blueberries are also grown in flower pots or similar, suitable containers. Use larger flower pots – 60 cm (2 feet) in diameter and some 50 cm (20 inches) in height. Fill them with proper (acidic, well aerated soil, rich in humus and organic matter) soil with a layer of gravel on the bottom, for better drainage. Plant at most 2-3 blueberries (size dependent – but usually 2 plants are more than enough) per pot and be sure to water them regularly – during summer heat, practically on a daily basis, unless you have a dripping watering system implemented. If you have space, plant only one blueberry plant per 60 cm (2 feet) pot.
If the soil is rich in phosphorus, use of NPK fertilizer with nutrient ratio 12:4:8. If soil lacks phosphorus, then use fertilizer with the ratio 10:10:10. 30g of fertilizers are added per bush in the spring and 30g in the autumn after the harvest. The amount of fertilizer is gradually increased to 150 g per bush that reaches a height of 2.5 m. Of course, it is better to add mineral fertilizers more often in smaller amounts to avoid spikes in nutrients and to lessen danger of causing root burns.
If possible, use more expensive NPK fertilizer optimized for berries with gradual (slow) release of nutrients – such fertilizer feeds the plants up to 4 months. Also, adding humus and mulch enriches soil even more and keep acidic level in check.
During the first year, don't apply nitrogen fertilizer – due to the roots sensitivity to such fertilizer. In a second year, one can add nitrogen rich fertilizer to promote growth of green mass, but it is better to use balanced fertilizers that are often rich in required microelements. Note that decomposing sawdust mulch 'demands' nitrogen as it decomposes – some gardeners are avoiding sawdust as a mulch and use another organic matter as mulch, or use mulch only during winter as protection from the cold.
If there is a drought, especially during long summer days, plants must be regularly watered, especially the young plants. Mounded blueberries or those that are grown in raised beds have good drainage, so overwatering is usually not as big problem. But overwatering leads to waste of water and nutrients and leeching of various chemicals into the soil. Some gardeners combine moisture sensors at 15 cm and 30 cm (6 and 12 inches) in the soil with water pump controller – this system prevents drying out and overwatering of plants and provides almost ideal growing conditions for blueberries and other plants in general. We don't have to mention that this system costs some money, right?
In small gardens, it is easy to spot lack of moisture on the plants – if they don't grow as expected, water them more often with more water per plant. Also, feel free to use hydroton pebbles in soil mix in flower pots for blueberries – these pebbles are pH neutral and can soak up moisture. As they release moisture, air enters the soil and helps the soil to 'breathe'.
The first year after the planting, flower buds are removed. When the plants reach a height of 1 to 1.5 m (3-5 feet), pruning is required in order to renew fruit branches. First, completely remove old, weak and diseased branches. Also, remove branches that have grown during the last two years and which brought the yield. New shoots will appear below the cut.
Note that period of growth and development of blueberry from the opening buds in early April to the stage of developed green fruits at the end of May is very sensitive. For these two months, presence of water and nutrients, with proper temperature has direct impact on the quantity and quality of fruits.
A particularly sensitive stage of development of the blueberries is flowering. Blueberries have a large number of flowers (each shrub can have 2000-3000 individual flowers) and the presence of numerous bees and bumble bees is required for pollination. Imagine 2000 bushes per hectare – bees must visit millions of blueberry flowers. Some varieties of blueberries are less attractive to bees (for example – Duke variety) than others (for example – Weymouth variety), depending on the quality of nectar, flower color and sugar content. It is recommended, even in small garden, to mix several varieties for several reasons like better pollination and longer harvesting season. Also, some varieties are more resilient than others on various diseases and pests.
Harvesting and Storage of Blueberries
The harvest lasts 6-8 weeks, and it depends on the chosen varieties and growing conditions. The harvest lasts 6-8 weeks, which, of course, depends on the variety and climatic conditions. Berries do not mature at the same time – on the same branch one can often find fruits in various maturation stages:
- immature green,
- green pink,
- blue pink,
- ripe fruit.
During harvest, one should be very careful in order not to damage the fruits or plants.
Blueberries packed in small shallow plastic pots can be kept refrigerated for 3-4 weeks at a temperature of 0°C - 2°C (around 33°F) at a relative humidity of 85-90%. In home gardens, they should be consumed right after picking – this way they lose almost nothing of their aroma and fragrance.
Growing Blueberries - Useful Tips
- Do not plant blueberries along walls or masonry fence! During rain lime from the wall will drain into the ground and make it alkaline and blueberries in this case will fail. If you really want to grow them on such positions, check pH on monthly basis on several depths and when required ('when', not 'if'), add compounds to increase acidity of the soil.
- Although single blueberry plant can pollinate itself, in order to improve the yield, it is recommend planting several varieties - combine different varieties next to one another, if you have no issues with, for example, prolonged harvesting season and similar.
- Blueberries should be exposed to the bees when quarter of flowers is opened, or even sooner. If backyard garden, there are always bees and similar insects flying around and this is not so much important.
- Every five years, it is good to remove the outer part of the blueberry shrub. If such blueberries is grown on raised bed, it is also a good time to renew the top soil, change planks (if needed) and do other maintenance jobs on raised bed.
- In windy areas, blueberries should be protected from wind gusts.
- The soil around blueberries should regularly be cleaned from weeds – they consume nutrients, moisture and can decrease fruit yield.
- Although blueberries are very resilient plants, they need protection from diseases and various pests - many birds love ripe blueberries and in such cases only protective nets can solve, or at least, mitigate problem of birds.
Long story short - blueberries should be part of any home garden. They are easy to grow - one just needs to know what they need in order to have long harvest of great tasting, very aromatic berries. When growing blueberries, proper pH is of utmost importance, so be sure to always have test kit around.