A guide to growing blueberriesPosted on: 06 July 2010 by Mark O'haire
All you need to know to grow the fragrant fruit successfully in your garden.
American high bush blueberries (Vaccinium corymbosum) are branching, deciduous shrubs that provide interest for much of the year, with their white bell-shaped flowers, dusty blue fruits, and spectacular autumn colour.
Some cultivars reach 2m (6ft). Blueberries need a light, free-draining, acid soil of pH 4-5.5. They prefer sun or partial shade and are relatively frost-hardy. Provide shelter from cold winds.
A Heavy Crop
Borne on large, attractive bushes, blueberry fruits are rather bland to eat fresh, but keep well even in the freezer. When cooked, they make deliciously aromatic muffins and jam.
For regular, heavier crops, plant more than one cultivar because they are only partially self-fertile.
Blueberries may be planted as freestanding bushes, as part of a hedge, or in a container.
Soil pH is critical, so prepare for planting well in advance. Neutral to alkaline soil can be acidified, but this is laborious and hard to maintain. To lower the pH of alkaline soil, add peat, sulphur (as flowers of sulphur), and sawdust individually or as a mix. Peat can be added to the planting hole prior to planting; dig in the other additives a year before planting. Application rates depend on soil type and pH. Sawdust needs nitrogen to decompose, so reduces the amount in the soil. Add sulphate of ammonia at 15g/sq m 1/2oz/sq yd) annually to counteract this.
'Berkeley' Large, firm fruits with a sweet flavour. Golden stems in winter.
'Bluecrop' Best all-round cultivar with large, mid-season fruit of good flavour.
'Coville' Medium yields of very large fruit on large, spreading bush.
'Herbert' Very large, late fruit. High yields from a large, spreading bush.
Alternatives to aciditying soil are to use a raised bed or container.
A raised bed, 15-20cm (6-8in) high and 1.5m (5ft) wide, aids drainage on badly drained soils and can be filled with peat-based compost. Peat substitute may have a high pH, so add flowers of sulphur to lower it.
In pots, use an ericaceous compost with grit added.
Container-grown blueberries often establish more quickly than bare-root ones. Plant from autumn to spring. Space bushes 1.5m (5ft) apart. If planting in a container, start with a 2 litre (3 1/2 pint) pot and pot on in later years.
Pruning & Training Blueberries
Prune after leaf drop. Follow the method for blackcurrants, pruning at soil level to encourage strong, new shoots.
Cut one or two unproductive branches to soil level each year, ideally in early spring when flower buds are obvious.
After pruning, apply a balanced compound fertilizer plus extra nitrogen (sulphate of ammonia) at 15g/sq m (1/2oz/sq yd).To maintain a low pH and suppress weeds, mulch in mid-spring with a 8-15cm (3- 6in) layer of acidic material, such as bark, old pine needles, or peat. If chlorosis shows in the leaves, top-dress soil with flowers of sulphur to lower the pH.
Maximizing The Crop
Fruit buds are considerably fatter than growth buds. When pruning, learn to recognize and retain branches bearing more fruit buds since they are likely to crop more heavily. Prune out branches with a larger proportion of growth buds so that the plant's energies go into producing fruit, not foliage.
Blueberries need copious amounts of water, preferably rainwater, which is acidic. Apply 50 litres/sq m (11 gallons/ sq yd) at each watering. If you have to use alkaline tap water, monitor its effect on the soil, adjusting the sulphur top-dressing as needed. Raised beds demand more water.
During flowering, either provide frost and wind protection in the form of fleece or plastic sheeting, or bring plants in containers under cover.
Repot blueberries in containers every two years in autumn. The largest size you should need is a 50 litre (11 gallon) pot for a bush about 1.5m (5ft) tall.
Take 10-15cm (4-6in) cuttings of soft, healthy growth in midsummer. Trim off the lower leaves. Insert the cuttings into pots of one part peat and three parts coarse sand and place in a propagator.
Once they have rooted, transplant into pots, harden them off, and give a high-potash feed every ten days.
Plant in their final positions after about a year.
Harvest from late summer to early autumn. A bush will yield 2.25-5kg (5-11lb). Pick berries by gentle pulling.
Birds, botrytis, and chlorosis may cause problems.
This extract is taken from The Royal Horticultural Society Vegetable & Fruit Gardening, published by DK, available at all good bookshops, RRP £20, or online from Amazon for £13.99.
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