Blueberries: profile, origin & winter hardiness
Blueberries are ideal for snacking on hot summer days. Wild blueberries can be picked in the forest – it is even easier to plant cultivated blueberries in your own garden.
Blueberries (Vaccinium spec.), also known as bilberries, have always been a big hit in the kitchen and are popular in desserts thanks to their sweet taste and strong colour. The low-calorie blueberry can be grown in your own garden with a little skill and will then provide high yields for years. We answer all your questions about blueberries and show you how you can grow the popular berry yourself.
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Blueberries: Profile and properties
Blueberries are a genus within the heath family (Ericaceae). These are found in many varieties worldwide, but especially in the Northern Hemisphere. All species of Vaccinium are woody shrubs. In this country, the wild wood blueberry (Vaccinium myrtillus) is only found in forest and moorland areas with acidic soil. For cultivation, on the other hand, cultivated blueberries were bred, descended from the American blueberry or Highbush blueberry (Vaccinium corymbosum) and into which a number of other species of Vaccinium were also incorporated. Almost all varieties available today are man-made species hybrids that have been adapted to our requirements in terms of yield, taste and fruit size. In contrast to the native blueberry, which measures about 0.5 m in height as a dwarf shrub, the cultivated blueberry can reach up to 4 m in height. The fruits of the cultivated blueberry are larger than those of the forest blueberry and do not grow individually but in clusters.
Tip: As blueberry roots do not have root hairs, they find it more difficult to absorb nutrients and water. Blueberries are therefore particularly sensitive to drought. In addition, the blueberry does not tolerate stagnant moisture or alternating humidity.
Is there a difference between blueberries and bilberries?
No, “blueberry” and “bilberry” are two common names used to refer to different species of Vaccinium. However, these everyday terms are not only assigned to a specific species.
Where do blueberries grow?
Just like the forest blueberry, the cultivated blueberry thrives best in a location with an acidic and moist soil environment. Blueberries do not grow at all, or at least not well, in loess or clay soils, which almost always have pH value that is far too high. To recreate the ideal soil, use acidic, humus-rich substrates in cultivation. Our Plantura Organic Ericaceous Compost is excellent for blueberries due to its low pH, and also has a smaller CO2 footprint than other soils due to its reduced peat content. In contrast to forest blueberries, cultivated blueberries need a full sun location.
- Perfect for acid-loving plants such as hydrangeas, rhododendrons, blueberry bushes, azaleas & more
- Ensures all-round healthy plants with lush blooms and aromatic berries
- Peat-reduced & organic soil: CO2-saving composition
Blueberry blossom
Blueberries set buds for flowers in the previous year. The flower buds develop laterally – at the side – or terminally – at the tips – on the one-year-old long and short shoots. Most of these fruit-bearing short shoots are on two- to three-year-old scaffolds. Their flowerheads are racemose, i.e. they have a main axis and grow in a raceme, with the individual flower heads nodding. In the first two weeks of May, blueberries start to blossom and you can see bell-shaped, white flowers that are swarmed by bees and other insects. The blueberry flowers are up to 20 mm long and have a slightly domed corolla of 5 fused petals. Each flower has 8 to 10 stamens at the base of the calyx.
Blueberry fruit
Blueberries ripen from the top down to the base. The fruit skin of the cultivated blueberry can be light blue, bright blue to black-blue. Their surface has a white bloom. This coating on the blueberry is caused by microscopic wax particles that form in the outermost cell layer of the fruit skin, are carried to the surface and deposited there. Its function is to protect the fruit from drying out, so it should not be wiped off. The fruit size of cultivated blueberries varies greatly between varieties. It is on average 5 to 12 mm high and sometimes up to 30 mm wide. Only after the berry has taken on its blue colour through and through and has remained hanging for another few days should it be harvested. In the period from July to September, the fully ripe fruits can be eaten.
Tip: As blueberries are so-called climacteric fruits, they can still ripen off the bush if they are not quite ripe, just like bananas, apples and pears.
What do blueberries look like inside? The flesh of cultivated blueberries is whitish, almost transparent and contains 30 to 80 tiny seeds. Forest blueberries have a dark blue interior.
Overwintering blueberries
Wild blueberries are well protected from the weather in their forest soil, whereas cultivated blueberries in beds or tubs need some winter protection on frosty days.
Are blueberries hardy?
In principle, blueberries are hardy down to a temperature of about -16 °C and can overwinter outdoors. However, they are susceptible to late frosts, which can damage the flowers. Young plants are also partly at risk for frost damage to young wood. Therefore, the right location and the timing of an application of potassium-rich fertiliser are important so that the blueberry makes it through the winter as well as possible. You can find out when and how best to fertilise blueberries in our article on feeding blueberries.
Winterising blueberries
To protect the cultivated blueberry from possible heavy frosts, a layer of straw, bark mulch or a fleece mat is ideal.
Overwintering blueberries in pots
To prevent frost from damaging the roots of the blueberry in the pot, you can wrap the pot with fleece or place it in a frost-free room. Nevertheless, care should be taken that the temperatures in winter are not too warm so that the blueberry sprouts healthily again in spring. As a woody plant of temperate latitudes, it needs a longer-lasting cold stimulus to ensure that it sprouts and flowers normally again in spring when the weather is good. In winter, conditions between 0 °C and 7 °C are therefore best if you overwinter the potted plant with some form of protection.
The aromatic berries of the blueberry are a real treat in summer. In our article on planting blueberries you will learn how you can also cultivate the fruit in your garden.
