It surprises me not, that only about two percent of gardeners grow currants although quite a few had grown them in the past. The reason for this is mainly because the cultural requirements are somewhat misunderstood.
There is also, from the amount of feedback I got, a currant fruit worm, which attacks the fruit itself. The fly lays eggs on the fruit as it begins to ripen. It manifests itself by the discoloration of only a few berries, a dull whitish pink, in only a few red currants and a premature coloring of gooseberries. This can be managed by either clipping the affected berries out or by a light application of an organic pesticide at flowering time. Remay has also been effective by excluding the fly. If you experienced powdery mildew in the tips it is best to clip them out. The best timing for this is when the first red currant becomes red.
When small shot holes are seen in the leaves you know there are sawfly worms present. Usually when things warm up in June. They can be easily pinched if done early. Otherwise growing gooseberries requires the same culture as currants. The pruning techniques differ somewhat. The main consideration is access for your hands to pick the fruit without tearing your skin on the very sharp thorns and to remove worn out wood; bull canes and any sucker growth from the base of the shrub.
Both currants and gooseberries are highly valued for their vitamin “C”content and juice or jelly production. This fruit is expensive to buy and it is highly valued in Western Europe. Our climate is very suitable to grow them.
Thornless Black Berries. I grow the Chester Thornless, which produces a very large crop of much larger but more acidic and less sweet than the wild berries. The canes are very vigorous, standing to 3 m tall with unusually long side shoots. The canes and side shoots are cut at 2 m tall and .5 m long in the fall to prevent winter damage and the side shoots are cut in February to 30 cm. All previous years’ fruit bearing canes are removed to ground level. The only problem is that these plants get so heavily laden that they need a strong 2.0 x 2.0 meter form of wire trellising even though they have an erect growing habit. The berries are about double the size of and slightly tougher skinned than the Himalayan wild blackberries. These berry plants need a sunny well-drained site. The big plus is that they are thornless and very easy to pick they are relatively pest free. There are better varieties than Chester; check with your garden centers. Personally I use them to balance the low acid wild blackberries, which only contain about 25 grams/liter, compared to the Chester’s 75 grams/liter. All berries respond well to the Fruit Tree & Berry food 5-10-15.