Welcome to Top of the Crops! Today, you will learn everything that there is to know about how to grow blueberries, and growing blueberries in a polytunnel. Prepare for bountiful fruit punnets from this expert guide on blueberry growing. And for more insightful gardening tips, check out our blog Polytunnel Gardening.
Blueberries are popular for their healthy nutritional profile and for their flavour. Though not a native fruit in the UK, blueberries can be successfully grown here in a fruit cage or polytunnel garden.
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Blueberries are the fruits of several species in the Vaccinium genus native to North America. These are not native to the UK, but are related to our similar native bilberries, called blaeberries in Scotland and by several other names in different parts of the country.
Blueberries do have specific needs when it comes to their environment – especially when it comes to the soil. But their needs can relatively easily be met in many British gardens.
In order to grow well in a garden, blueberries need:
Full sun.
Acidic soil or ericaceous growing medium with a pH of 4.5–5.5, with plenty of organic matter.
Making sure that you meet the above environmental needs are the most important things in growing blueberries successfully. The right location with sufficient sunshine and the right acidic soil or growing medium are crucial for these fruiting shrubs.
Blueberries can be grown in the ground, in raised beds, or in containers.
If you already have acidic soil in your garden and are looking for acid-loving plants, then of course blueberries are a good option to consider.
If you do not have acidic soil in your garden then you may sometimes wonder about amending the soil in a certain growing area in order to grow blueberries and other plants that like acidic soil.
If your soil is neutral or already somewhat acidic, you can potentially amend it by adding sulphur and by adding plenty of acidifying organic matter such as pine needles, conifer bark, leaf mould etc...
However, rather than trying to alter the soil in your garden, it is generally best to select plants suited to the soil you have. Any plants like blueberries that need special conditions can always be grown in raised beds or containers.
Raised beds or containers for blueberries should be filled with ericaceous soil or potting mix. You can either purchase this or potentially make your own using natural materials.
Blueberries can be planted out or potted up at any time of the year. Bare-root plants can be purchased over the dormant period through the winter months, and pot grown specimens are available at other times.
Bare root specimens are generally cheaper, and will usually establish most successfully when planted out into a garden. Late autumn and early spring are the best times to plant, as conditions will be ideal for establishment during these times.
If you are planting blueberries into the ground or a raised bed, make sure you have chosen a site that is sunny and sheltered. Blueberries can cope with light or dappled shade but will fruit best and have the best autumn colour in a sunny spot.
To plant a blueberry bush:
Dig your planting hole, as deep as the existing root system and around three times as wide.
Place the blueberry bush into the hole, spreading out the roots and making sure it is level.
Gently firm the soil back around the roots, making sure the plant sits at the same level that it was at in its previous position.
Water your new shrub in well.
Add an organic, ericaceous mulch around the base of your new blueberry plant, but make sure that it does not touch the stems.
If you are adding more than one blueberry bush, these should usually be planted 1-1.5m apart, depending on their eventual size.
If you are planting blueberries in a container, a young plant will need a pot at least 30cm across, and a larger one will need a pot at least 45-50cm in diameter.
Add some ericaceous compost to the base of the container. Place the blueberry bush within it. Firm more compost around the root ball, then water well, making sure excess water can drain away freely from the base of the pot.
Blueberries are not challenging to care for and when they are grown in a suitable spot they can be low-maintenance plants. However, you do need to spend some time on care, especially if you are growing blueberries in pots or other containers.
If you are growing in the ground but not growing in naturally acidic soil you will need to think about maintaining soil acidity over time. This might mean testing and adding sulphur. But it can also simply be a case of adding acidic mulches, ericaceous organic fertilizer, and watering with rainwater over time.
In pots filled with ericaceous potting mix, you will need to make sure that you replenish that growing medium as time goes by. You should repot blueberries every 2-3 years with new ericaceous compost. Again, when growing in containers, remember to water with rainwater not tap water whenever possible.
Remember to water with rainwater as much as possible, rather than using tap water which may often be too alkaline. Of course this is especially important in hard water areas.
When watering, aim to keep the soil or growing medium moist but not saturated. Don't allow waterlogging to occur as this can cause a range of issues.
Blueberries growing in the ground don't usually require feeding. Healthy soil and an ericaceous organic mulch laid upon planting and replenished each spring should provide for these plants' nutritional needs.
Blueberries in containers, however, do require additional feeding. It is best to feed your pot grown blueberries with a specialist organic, ericaceous plant feed every month or so through the growing season between April and September.
The best mulches for blueberries include pine needles, conifer bark or wood chips, and leaf mould – especially leaf mould made with more acidic leaves. It is best to avoid the use of more alkaline organic matter such as well rotted manure and mushroom compost.
Some but not all blueberries are fully winter hardy. Make sure that you check the hardiness rating of the variety or varieties you wish to grow. Many recommended for UK gardens are H6 hardy, and will make it through the winter unscathed.
However, when grown in containers, blueberries can be more vulnerable to the cold and it can be a good idea to provide some extra protection. Wrap the pots to protect the roots, and/or move pots to a more sheltered location.
If a late frost threatens, this could damage the blueberry flowers. Avoid damage by covering the plant with fleece or other material if the weather forecast shows this threat.
Repot small blueberry plants into a larger container when roots emerge from the base of the pot. And repot larger plants into the same container with new ericaceous potting mix every 2-3 years.
Deciduous blueberry species that lose their leaves in winter are best propagated by means of softwood cuttings taken in late spring or semi-ripe cuttings taken late in June or in July. The latter option is best for evergreen species.
You likely won't need to prune blueberries for their first couple of years. After this, pruning should ideally be undertaken in late February or early March. When pruning, the goal is to retain branches with plenty of fruit buds while maintaining an open-centred framework.
When pruning, aim to:
Remove any dead, damaged or diseased material or rubbing branches.
Cut back twiggy growth at the branch ends to a strong, upward-facing branch or bud to encourage side branching.
Get rid of around ¼ of the oldest woody material, to encourage new productive shoots from the ground or low down near the base.
Berries will mature from a green to a dusky blue once they are ripe. The berries will not all ripen at the same time so you will need to check the plants regularly and pick the berries over several weeks.
By the time a blueberry bush is around 7 years old, it should produce between 2.5 and 5kg of blueberries each year while in peak productivity.
Some good blueberry varieties to consider growing in the UK are:
As long as they have the sunshine and soil conditions they need, blueberries are generally trouble free on the whole. However, problems like powdery mildew, aphids and vine weevils can trouble young plants.
Another issue that can arise is chlorosis, which can cause the leaves on a blueberry plant to turn yellow and which can even kill plants if left untreated. This is usually a sign of a problem with the pH of the soil or growing medium.
Birds can also often be a problem, eating all the fruits before you get the chance to harvest. This is why growing in a polytunnel or fruit cage can be a good idea.
Ensure that pollinators can reach blueberries while they are in flower when growing undercover.
Companion plant to attract pollinators and other beneficial wildlife, to repel, confuse or distract pest species, and to provide other benefits within the garden ecosystem.
Blueberries are shallow rooted and so it is important to take care about what grows close by. However, creating a guild of beneficial plants around a blueberry patch can help to attract pollinators in the spring, and help with organic pest control.
The main thing to remember when choosing companion plants for blueberries is that any companions will need to share the blueberries love for acidic conditions.
You might consider some spring-flowering acid-lovers like azaleas, heathers, rhododendrons, and spring bulbs like grape hyacinths, or spring flowering irises, for example.
Around the sunny side of blueberry bushes, you might also consider planting some strawberries, which can cope with the acidic conditions, and herbs for pest control like rosemary and thyme... to give a few examples.
Baker, R. (2023) Why Blueberry and Strawberry Plants Are Excellent Garden Companions. House Digest. [online] Available at: https://www.housedigest.com/1435998/blueberry-strawberry-companion-plants/ [accessed 15/12/23]
