Blueberries

Blueberries produce not only delicious fruits, but also attractive spring flowers and vivid foliage in autumn. The sweet, juicy fruits are rich in antioxidants and great for eating freshly picked or for adding to smoothies and desserts. Best suited to acidic soils, these shrubs can be grown in the ground or in large containers of ericaceous compost. Compact varieties are ideal for small gardens.

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Grow

Grow

Watering

Keep the compost or soil moist at all times, but not soaking wet, throughout the growing season.
Water blueberry plants with rainwater, not tap water, unless you have no alternative in a drought. Tap water will raise the pH level and blueberries like acidic conditions.

Feeding

Plants in containers should be fed every month through the growing season (April to September) -  using a liquid fertiliser specifically for ericaceous (lime-hating) plants, following the manufacturer’s recommendations.
With blueberries growing in peat-free multi-purpose compost, you may need to add chelated iron regularly to avoid chlorosis.

Plants in the ground don't usually need feeding apart from an annual ericaceous mulch and a high nitrogen feed, such as sulphate of ammonia, in late winter – apply at a rate of 15g (½oz) per square metre/yard.
But if plants aren’t growing well, apply a fertiliser designed for ericaceous plants. Avoid overfeeding, as blueberries are sensitive to high fertiliser levels. Poor growth may be a result of high pH, excess nutrients and fluctuations in soil moisture.

Maintaining soil acidity

Ensure the soil stays at pH of 5.5 or lower, to avoid problems. Check the pH of your soil in spring and add sulphur chips if it needs lowering. This shouldn’t be necessary with container-grown plants provided ericaceous (acidic) fertiliser and rainwater are used.

Mulching

Mulch plants in the ground in spring or autumn with 7–8cm (2½–3in) layer of acidic or neutral organic matter, such as composted sawdust, composted or freshly chipped pine bark, composted pine needles or leafmould. Avoid manure and mushroom compost, as they tend to be quite alkaline.

Winter protection

Not all blueberry cultivars are fully hardy, and even hardy plants can be damaged by a combination of low temperatures and wet conditions, especially if growing in a container. So move containerised plants into a shed or garage during prolonged cold spells, or wrap the pot in hessian or bubblewrap to protect the roots.
Protect flowers from late frosts in spring with a double layer of horticultural fleece.

Re-potting

Blueberries growing in containers of soil-less ericaceous (acidic) compost often require annual repotting, as soil-less compost tires quickly and loses its structure, leading to root damage. It’s best to choose a soil-based ericaceous compost instead.

Young plants that are initially planted in a 30cm (1ft) wide container should be repotted into 45–50cm (18–20in) once roots appear through the drainage hole in the base. 

Propagation

Evergreen species grow better from semi-ripe cuttings, taken in late June to early July. Deciduous species can be propagated from softwood cuttings taken in late spring or semi-ripe cuttings taken in late June to early July. 

Pruning

Pruning is rarely needed in the first two years, just remove any crossing or misplaced branches.
After that, prune at any time during the dormant season (November to March), but ideally in late February or early March when fruit buds can easily be distinguished from leaf buds. Fat buds produce flowers and fruit, while smaller, flatter buds form shoots and leaves.

A mature bush should contain about one-third old, one-third middle-aged and one-third young stems.
Prune out:

  • Dead, diseased, dying, weak, rubbing or damaged stems, plus any that are touching the ground 
  • Twiggy growth at the ends of the branches that fruited last year, cutting back to a low strong, upward-facing bud or branch 
  • Remove up to a quarter of the oldest and thickest stems at the base of a mature plant or prune to a younger strong shoot lower down on the branch

In Scotland and colder parts of northern England, fruit growth produced in the summer may fail to ripen, with stems dying back to leave hollow wood and dead tips. In this case, cut back the affected shoots to healthy wood, 15cm (6in) from the base.

Read more about pruning and growing blueberries

Plant

Choosing blueberries

The most widely grown blueberries are cultivars of northern high bush blueberries (Vaccinium corymbosum), which are branching, mainly deciduous shrubs reaching up to 1.5–1.8m (5–6ft) tall. Apart from producing fruit they are ornamental, with bell-like flowers in spring. The foliage has good autumn colour. Half-high blueberries are hybrids between V. corymbosum and low-bush V. angustifolium, making more compact plants, about 50–120cm (20in–4ft).

There are many excellent varieties to choose from – look for those with an RHS Award of Garden Merit (AGM), which shows they performed well in trials, so should grow and crop reliably. See our list of AGM fruit and veg.
Although many blueberries are partly or fully self-pollinating, it is best to grow two or preferably three different cultivars, as cross-pollinated plants tend to produce more abundant crops.

Where to plant

Blueberries need a sheltered site in sun or part shade, with well-drained but moisture-retentive, acidic soil (pH 4.5–5.5), that does not dry out in the summer or become waterlogged in the winter. If you can grow azaleas, rhododendrons and camellias in your garden, blueberries should be successful too. Test your soil pH if you are unsure – easy-to-use kits are available in most garden centre or online.

If your soil is only slightly acidic, you can try acidifying it to lower the pH to a suitable level by adding sulphur chips. But this would have to be done in advance, ideally the previous summer or autumn.

If you have heavy clay or alkaline soil, it is best to grow blueberries in large containers or raised beds filled with ericaceous soil or soil-based John Innes ericaceous compost. If you use soil-less ericaceous compost, ideally
choose peat-free, but you may need to add chelated iron regularly to avoid chlorosis. If growing in a container, choose a compact blueberry variety and a large container at least 30cm (12in) wide.

How to plant

Improve your soil before planting by digging in plenty of bulky, acidic organic matter, such as pine needles, leafmould, composted conifer clippings or bracken. Avoid well-rotted farmyard manure or mushroom compost, which are too alkaline for blueberries.

Blueberries are easy to plant in the ground:

•    Water the plant thoroughly
•    Dig a hole a little deeper than the pot depth and three times as wide 
•    Tip the blueberry out of its pot and tease out the roots if compacted 
•    Stand the plant in the hole and adjust until the surface of the compost is level with the soil surface 
•    Backfill around the roots with soil, firm in and water well 
•    Spread a thick layer of ericaceous mulch, such as pine bark (composted or chipped) or leafmould over the          soil, leaving a gap around the base of the stem
•    Space high-bush cultivars with 1–1.5m (3¼–5ft) all round, and half-highs with about 1m (3¼ft) all round.

Also see our step-by-step guide to planting shrubs such as blueberries https://www.rhs.org.uk/advice/how-to-plant-a-shrub

To plant in a container:

•    Water the plant thoroughly
•    Choose a large container – at least 30cm (12in) in diameter for a young plant, 45–50cm (18–20in) for a               larger plant
•    Half-fill with ericaceous (acidic) soil-based compost
•    Remove the blueberry from its original pot and stand it in the new container. Ensure the plants sits at the           same level as in its previous pot.
•    Fill around the rootball with more compost, firm down and water in well

Find out more about growing fruit in containers

Common problems

Birds
Birds

Birds, especially pigeons, can cause an array of problems including eating seedlings, buds, leaves, fruit and vegetables.

Remedy

Protect the plants from birds by covering them with netting or fleece. Scarecrows and bird-scaring mechanisms work for a while, but the most reliable method of protection is to cover plants with horticultural fleece or mesh.

Powdery Mildew
Powdery Mildew

Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.

Remedy

Keep the soil moist and grow in cooler locations.

Aphids
Aphids

Look for colonies of greenfly on the soft shoot tips of plants or on leaves. They suck sap and excrete sticky honeydew, encouraging the growth of black sooty moulds.

Remedy

Use your finger and thumb to squash aphid colonies or use biological control in the greenhouse.

Harvesting

The berries start to ripen from mid-summer onwards, changing from green to dusky blue when ready to pick. They won’t all ripen at once, so check over plants several times. A fully productive plant, around seven years old, will produce up to 2.25–5kg (5–11lb) of blueberries.

Blueberries can be eaten fresh or can be dried, frozen, made into preserves or used in cooking. They are rich in antioxidants and vitamins (especially vitamin C).
 

Recommended Varieties

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