Blueberries

Blueberries produce not only delicious fruits, but also attractive flowers and vivid autumn colour. Best suited to acidic soils, they can be grown in the garden or in containers.

Vaccinium corymbosum  'Nelson'

Quick facts

Common name Blueberry
Botanical name Vaccinium corymbosum, V. angustifolium
Group Fruit; shrub; evergreen or deciduous
Fruiting time Mid-summer to early autumn
Planting time November to March
Height and spread 45cm-2m (18in-7ft) height and spread
Aspect Open, sunny, sheltered
Hardiness Frost hardy to fully hardy
Difficulty Moderate

Cultivation notes

The most widely grown blueberries are cultivars of northern high bush blueberries (Vaccinium corymbosum), branching mainly deciduous shrubs reaching up to 1.8m (6ft) in height. Apart from producing fruit they are ornamental, producing bell-like flowers in spring. The foliage has good autumn colour. Half-high blueberries are hybrids between Vaccinium corymbosum and low-bush Vaccinium angustifolium, making more compact plants.

Blueberries need a sheltered site in well-drained, moisture-retentive, acidic soil (pH 4.5-5.5) in sun or part shade. If you can grow azaleas, rhododendrons and camellias in your garden, blueberries should be successful too. Check your soil pH if unsure.

If your soil is only slightly acid, you can try acidifying it to lower the pH to the optimum level for ericaceous plants. However, this would have to be done in advance, ideally the previous summer or autumn.

If you garden on heavy clay or alkaline soils, it is best to grow blueberries in containers. Improve the soil before planting by removing all weeds and incorporating lime-free soil improvers such as composted bark, bracken, leafmould, pine needles or composted sawdust to a fork’s depth. Avoid adding manure or mushroom compost which are too alkaline for blueberries.

Highbush blueberries can reach 1.5-1.8m in height and half-high about 0.5-1.2m. When planting, space highbush cultivars with 1-1.5m (3¼ft-5ft) all round and half-highs with about 1m (3ft) all round. Mulch newly-planted blueberries with pine bark (composted or chipped) or leafmould.

Container cultivation

If you do not have an acidic soil or garden on heavy clay, try growing blueberries in containers or raised beds  ideally filled with ericaceous soil. If this is not easy to source, RHS members report John Innes Ericaceous potting compost to be a suitable alternative.

When using soil-free media (multipurpose compost), ideally choose a peat-free one, but be aware that peat-free media might require frequent use of chelated iron to avoid chlorosis. Pot-grown blueberries in soil-less growing media often require annual repotting as the compost tires quickly, even if it means changing some of the old compost with fresh and putting the plant back into the same pot. This is because the soil-less potting media loses its structure quite quickly leading to root damage or rot.

Pollination, fruiting & harvesting

Although many blueberries are partly or fully self-pollinating, it is best to grow a minimum of two, cross-pollinated plants tend to produce larger fruit. To achieve this, plant two or preferably three different cultivars to ensure reliable, abundant crops.

Pick fruit when it is completely blue and has a white surface bloom. Fully productive plants around seven years old produce up to 2.25-5kg (5-11lb) of berries.

Watering and feeding

During dry spells water blueberries with rainwater, not with tap water, unless you have no alternative in a drought.
If growing in containers keep the compost moist but not waterlogged and don’t allow the compost to dry out between waterings. Feed container plants every month using a liquid fertilizer formulated for ericaceous (lime-hating) plants, following the manufacturer’s recommendations.

Mulch plants in open 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.

At Wisley, blueberries, need minimal feeding apart from supplementing annual additions of organic matter with 15g per sq m (½oz per sq yd) of sulphate of ammonia sprinkled round the plants in late winter. If plants are not growing well try an application of fertilizer recommended for ericaceous (lime-hating) plants as directed by the manufacturer. Avoid overfeeding, as blueberries are sensitive to high fertiliser levels. Poor growth may be a result of high pH, excess nutrients (high soluble salts) and fluctuation of soil moisture levels.

Winter protection

Not all blueberry cultivars are fully hardy. Even hardy cultivars, as with many other plants, can be damaged in winter if exposed to a combination of low temperatures and wet conditions, especially if container grown. Move containerised plants indoors in 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 with a double layer of horticultural fleece.

Pruning and training

Blueberries fruit on short sideshoots produced during spring or early summer of the previous year. They can also form fruit buds on the second flush growth produced later in the summer, at the tips of strong shoots.

Pruning is rarely needed in the first two years, just remove any crossing or misplaced branches.

Prune any time over the dormant season (November to March), but ideally in late February or early March when the fruit buds can easily be distinguished from the 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 stems at the base of a mature plant or prune to a younger strong shoot lower down on the branch

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.

    Vaccinium corymbosum' Nelson'Blueberry blossomBlueberry plant in a potPruning a 3 year old blueberry bush

    Cultivar selection

    Northern highbush blueberries

    The cultivars listed below are arranged in the approximate order of ripening from July onwards, but the ripening will depend on the climate in the given year.

    Duke’ AGM - sturdy, upright, very hardy with good autumn colour. It flowers late, but ripens early making an ideal choice for areas with late frosts. Heavy cropping, though can lack vigor if not well fed and pruned. Mild flavour; keeps well

    ‘Spartan’ AGM – vigorous, upright and hardy. Late blooming, a good choice for areas with late frosts; good autumn colour. Particular about soils, needing organic rich, well-drained soil to flourish. Large fruit with delicious, tangy flavour

    ‘Patriot’ – smaller, moderately upright shrub. Prefers moister soils and is tolerant of heavier soils. Lovely red & gold autumn colour.  Large firm deep blue berries with an excellent flavour

    ‘Bluejay’ – Vigorous, producing strong upright stems. Hardy, flowers late. Attractive autumn color. Good flavour and reliable cropper

    ‘Bluecrop’  - vigorous,  upright hardy shrub, good autumn colour.  Reliable crops of large light blue firm, well flavoured berries. The main high yielding commercial variety

    ‘Toro’ - hardy, robust well-spaced growth. Both flowers that open pink and fade to white and the autumn colour is ornamental. Reliable cropper producing large berries

    ‘Hardyblue’ - large, upright, vigorous and hardy; a good choice for areas with late frosts and one of the best for heavier or less than ideal soils. Good autumn colour and red stems in winter. Sweet and high yielding

    ‘Herbert’ – moderately vigorous, open spreading and hardy. More fussy about growing condition. Large to very large fruit with excellent flavour

    ‘Bluegold’ – rounded, compact growth. Well suited for tubs. Heavy crops of good size, well-flavored berries

    ‘Chandler’ – vigorous, upright growth. Good autumn color. Reliable heavy yields of very large firm berries.  Fruit is ripening over period of four to six weeks

    Southern highbush blueberries

    ‘Ozarkblue’ – winter hardy, but better suited for warmer regions where it remains semi-evergreen. Vigorous plant, heat tolerant. Reliable crops of large, light blue fruit with excellent flavour. Late ripening

    Half-high blueberries

    ‘Northland’ – one of the hardiest cultivars. Spreading habit, more compact reaching up to 1.2-1.5m. Tolerant to wider range of soils. High yields of small juicy fruits with good flavour

    Links 

    AGM fruit and veg list
    RHS Find a Plant

    Problems

    Blueberries are usually pest and disease free, but can occasionally suffer from vine weevil, powdery mildew and  Phytophthora root rot. Birds can be a problem, protect the ripening fruit with netting.

    If grown on soils with higher pH the plans can suffer from chlorosis and require treatment with chelated iron.

     

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