To ensure your currant bushes bear fruit well and produce a bountiful harvest, care after harvest is crucial and should not be neglected. As soon as the bushes have produced their last berries, you can begin caring for them immediately, which will guarantee an excellent, bountiful harvest next summer.
Although currants aren't particularly fussy, they still require minimal care. Give them a little time, feed them, prune them, and treat them for pests, and they'll thank you with a bountiful harvest. Besides clearing fallen leaves in the fall to prevent pest larvae from overwintering, you should also prune old or damaged branches, remove any remaining mulch, and dig around the tree trunks to prepare the bushes for winter.
Additionally, pest prevention is essential. The bushes have already produced their berries, so you can safely treat them with, for example, a 1% solution of Bordeaux mixture, and repeat the treatment in a couple of weeks. All bushes should be treated, even if they appear healthy. If pests are spotted, more effective measures should be taken. If you notice glassworms in action, such as withering and drying twigs, remove them and burn them. Otherwise, the caterpillars will descend to the base and begin chewing through the bush in the spring, causing further damage.
If you spot mites or gall midges, immediately apply the appropriate treatments. For example, Neorot is effective against mites, and Kinmix works great against gall midges. Dilute these treatments according to the instructions, treat the plants, and your plants will survive the winter without a hitch, returning in the spring safe and sound, ready to bloom and produce a harvest.
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Now that we've completed our preventative maintenance, it's time to prune the bushes. We'll remove basal shoots to prevent the bushes from becoming too dense, trim away diseased branches, and remove damaged ones. By spring, our bushes will be slender and beautiful, with nothing to hinder their growth or shade the sun.
Now it's time to fertilize. Currants, like strawberries, begin to form buds for next year at this time. Therefore, next summer's harvest depends on fertilization. Organic matter and mineral complexes containing potassium and phosphorus are needed. You can apply fertilizer either with a complete complex such as Nitrofoska, or mix a spoonful of superphosphate with potassium, or urea with superphosphate, in a bucket of water, adding a glass of ash. Organic matter can be added in the form of chicken manure, diluted in 12 parts water, or mullein. The manure mixture is left to steep for a couple of weeks, then diluted with water (a liter jar per bucket). Furrows are made around the bushes and the mixture is poured into them. The mullein is diluted 1:1, left to steep for a week, diluted again 1:1, and watered.
Incidentally, feeding currant bushes with potato peelings is very beneficial. You can simply dig them in around the bushes. Currants also respond well to watering with a soapy solution (meaning laundry soap).
All these actions will strengthen and fertilize your bushes, and next year your currants will delight you with excellent flowering and a delicious, rich harvest.
See also: Siberian iris: planting and care in open ground.
At this time, you can dig in the young shoots. By spring, they will have taken root and can be replanted, thus increasing the number of bushes. Incidentally, this is how old currant bushes over ten years old are rejuvenated. In the spring, the old plant is removed, and the young, established bushes begin to grow.

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Features of planting currants in autumn
Blackcurrant: pruning in autumn, rejuvenating an old bush, preparing for winter
Currant pruning scheme in autumn for beginners