How to Grow Currants
Blackcurrants are hardy shrubs, easy to grow and long-lived in cool climate districts. The dark, acid berries are richer in vitamin C than almost any other garden fruit. Redcurrants and white currants are close relatives, although they have a different growth habit. They, too, are long-lived in the garden and highly productive.
Planning the crop
Currants thrive in full sunshine but also do well in slightly shaded sites. Avoid pockets and hollows subject to late spring frosts, which damage the flowers of red and white currants. Currants grow in any moist, well manured soil that isn't waterlogged.
How many to grow: A mature blackcurrant will yield 5-7 kg of fruit. A compact, fully grown bush will need an area of about 1.5 m in diameter. Red and white currants yield 4-5 kg. Mature bushes occupy 2-2.5 square metres; they can be cordon-trained.
The Ben varieties have revolutionized blackcurrant growing, bringing heavy crops, disease resistance and a more compact habit. The New Zealand-bred Blackadder is also excellent. But if space is no problem, choose from these three older varieties:
Wellington XXX: Midseason; heavy cropper; sweet fruits; do not spray with lime sulphur.
Baldwin: Late; medium-sized currants; compact bush.
Malling Jet: Very late; also flowers late so escapes frost.
For redcurrant varieties, Rovada, Laxton's No. 1 and also Red Lake are good. The most widely available white currant is White Versailles.
Buy certified disease-free plants from a reputable nursery. Enrich the soil well with compost or manure. Both red and white currants are susceptible to potash defi ciency, so for these plants also incorporate 30 g of sulphate of potash per square metre. Most plants are sold in containers so may be planted any time the weather is right. Even so, planting is still best done in autumn, while the soil is still warm enough to get the roots growing but watering is not usually necessary. Plant blackcurrants 1.5-1.8 m apart, red and white 1.5 m apart (if growing as cordons, space 40 cm apart).
Position compact varieties slightly closer. Place them in the ground a little deeper than they were in the container, using the soil mark on the stem as a guide. After planting, prune all the shoots to four buds above ground level, cutting just above an outward-facing bud. The bushes will then produce vigorous new growth that will provide a good crop in the second summer after planting. After this initial pruning, mulch with a layer of compost, manure or other organic material.
Repeat this every spring, at the rate of two buckets per square metre, to feed the plants and conserve moisture in the soil. Dress the soil in midwinter with 30g sulphate of potash per square metre and again in early spring with 30 g sulphate of ammonia. Every third year, apply 60 g of superphosphate per square metre. Or top-dress each spring with a general bush fruit fertiliser. After hard frosts, use your feet to firm in any bushes that have been lifted.
Don't disturb the roots by weeding with a fork or hoe; regular mulching should keep down weeds. Water regularly during dry periods. In the first autumn after planting, cut down the weakest of the current season's shoots to just above the soil level. The following autumn, cut out a few weaker shoots to stimulate new growth. During subsequent autumns, remove a proportion of the older wood to make way for replacement shoots. Cut low to promote new growth from near ground level; remove a quarter to a third of the old wood. Red and white currants are pruned to a goblet shape in both late winter and summer. In the second winter, shorten each branch by half. From the third winter, cut back leading shoots halfway and laterals to two buds. From the fifth winter, cut back all current season's growth by 2.5 cm and remove congested old wood from the bush's centre. Every midsummer after harvesting, cut back laterals to three to five leaves.
Raising New Bushes
It is easy to propagate blackcurrants from hardwood cuttings. In mid-autumn take cuttings of current season's shoots that are well ripened and look healthy. Cut off the un ripened tip just above a bud, and the bottom just below a bud, for a cutting about 20-30 cm long. Dig a 15 cm deep, V-shaped trench. If the soil is heavy, add a 5 cm layer of sand in the trench to improve the drainage. Push the cuttings into the trench, about 15 cm apart, with two buds showing above ground. Fill in the trench and tread the soil firm. Red and white currants can be propagated from well-ripened wood in autumn. Trim off any soft tips to leave cuttings 25-40 cm long. By the following autumn the cuttings should have rooted and be ready for their permanent positions.
Pests and Diseases
Pests include blackcurrant gall mite, aphids and capsid bugs. The diseases most likely to occur are grey mould, honey fungus (not in South Africa), leaf spot and reversion (blackcurrants only).
Harvesting and Storing
Pick blackcurrants only when they are properly ripe - a week or so after they turn black. The currants at the top of each cluster generally ripen first. Pick red and white currants as soon as they are ripe - cut off the entire cluster with scissors. Use them right away as they do not keep for long. All types of currants freeze well.