This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Except in pruning, everything we have said about Gooseberries in regard to their cultivation will apply to Currants. However, it may be as well to say that all Currants will thrive on northern or eastern aspects where but little sun reaches them. Black Currants especially do best on a border at the north or east side of a wall, although they will grow anywhere. Southern cultivators had better note, however, that warm soils and sunny aspects are the reverse of favourable to any of these fruits; and northerners may be glad to know that places too cold or damp for other fruits are just the best position possible for them.
In the matter of pruning, we prefer to keep the old branches of Red and White Currants well furnished with spurs, and to depend on these. To cause spurs to form freely, it is well to cut the annual shoots half-way back at each annual pruning while the bushes are young and in training. We prefer having them globe-shaped, for the same reason that we prefer Gooseberries to be so trained. After the bushes are large, pruning consists in cutting back all annual shoots to one or two eyes, but it is better still to pinch them to that while they are young. On good soil, bushes should ultimately attain from 6 to 8 feet in height; and bushes this size, when well furnished with spurs, generally bear a great quantity of valuable fruit. When birds are troublesome it may be necessary to protect the fruit by means of old herring-nets, which are to be had very cheaply. When the bushes are on borders beside walls this is easily done; otherwise, it may be necessary to put up a railing all round the quarter on which they grow to support the net. A few long poles in the centre will keep the net clear of the bushes. Where birds destroy the buds in winter and spring, pruning should be deferred until the bushes begin to grow.
To afford protection, the bushes should be liberally dusted in winter with a mixture of lime and soot.
Red Currants are very suitable for covering north or east walls. Four, six, or eight cordon trees are best for this purpose.
Black Currants must be pruned on a different principle, for the best of the fruit is borne on the preceding year's shoots, so pruning must be done in the same way as recommended for Morellos. No spurring in should be practised, but in its place a continual cutting back of old wood, and a continual encouragement of young. Learn the principle on which they should be pruned, and the practice will become easy. Crowding should be avoided, for crowding means small fruit, and small fruit is a great trouble to gather, and very inferior after it is gathered. Amateurs who are first-class pruners of Gooseberries, in their own opinion, generally consider the proper pruning of Black Currants an inscrutable mystery, and so leave them alone. Yet Gooseberry and Black Currant bushes should be treated very much alike, and that means that annually a thinning out in a regular manner should be given to each. It is bad pruning indeed that is not better than no pruning, for the letting in of air and sun works a wonderful improvement on these fruits, and the thinning-out causes greater vigour in the shoots left. For covering north walls which are under 8 feet in height, Black Currant bushes are admirably adapted.
In such positions they should be trained and treated in the same way as Morellos. The best white is White Dutch; the best red, Raby Castle, Red Dutch, and Magnum Bonum; and the best black, Black Naples and Lee's Prolific. There are many very inferior kinds of all the sorts in cultivation, and great care should be taken, when young plantations are made, to get the sorts we have recommended true to name. Gooseberries and Currants are very easily increased by cuttings. The time to put them in is early in October. The cuttings should be of the current year's wood, and 15 or 18 inches long. They should be pulled off the old bushes in a way to secure a thin section of the old wood. The ends should be smoothed with a sharp knife, the tips taken off the tops, and all the buds removed, except four at the top. Such cuttings, planted firmly, with a little sandy soil at the bases, on a shady border, 4 inches apart in the rows, and 15 between the rows, will root readily. Green-fly and caterpillars which attack Currants must be got rid of in the same way as advised in the case of Gooseberries. A. H. H.