Blackcurrant: growing, pruning & harvesting cassis
Blackcurrants are a popular garden berry. But what distinguishes blackcurrants from other currant varieties? How do you grow them? When is the best time to harvest blackcurrants? Find out everything you need to know here!
The blackcurrant is a unique currant species. Read on to discover what makes blackcurrant plants so special, how to grow and care for them at home and how to use them in the kitchen!
Contents
Unique characteristics of blackcurrants
Blackcurrant (Ribes nigrum), also known as black currant or cassis, are beloved berry bushes found in many gardens all over the UK. Blackcurrant bushes are native to the temperate latitudes of Eurasia, growing naturally from France to the Himalayas. Today, domesticated blackcurrant varieties are grown worldwide.
Blackcurrants are deciduous shrubs that are covered with dark purple berries in summer. Blackcurrant bushes grow up to two metres tall and grow three- to five-lobed leaves about the size of a hand on their shoots. Fortunately, despite belonging to the gooseberry family (Grossulariaceae), blackcurrant bushes are completely thornless, unlike many members of the gooseberry family.
When the blackcurrant flowers open, they emit their characteristic, tart, intense aroma. The deep purple blackcurrant berries are about the size of a marble and have a tart, sour taste that sweetens when ripe.
The difference between blackcurrants and redcurrants
Redcurrants are a popular relative of the blackcurrant. However, there are clear differences between the two. Apart from their distinctive colour, blackcurrants are also slightly larger than redcurrants and their chemical composition differs. In particular, blackcurrant fruits have up to five times more vitamin C than redcurrants.
Can you enjoy blackcurrants raw? Yes! Blackcurrants are perfectly fine to eat raw. However, because of their tangy flavour, they are often processed when sold. Processed blackcurrants are more palatable than raw blackcurrants but they also tend to have fewer nutrients. Redcurrants, meanwhile, are milder, and are more commonly enjoyed raw.
Unlike redcurrants, most blackcurrant varieties cannot self-pollinate. As a result, it is best to grow two blackcurrant varieties next to each other so that they can cross-pollinate and produce an abundant harvest.
Want to know more about the different currant species? We have got you covered in our currant overview, where you can learn all about redcurrants, whitecurrants and blackcurrants, from planting to harvest.
The best blackcurrant varieties
There are many blackcurrant varieties to choose from. Here are a few of the best:
- Blackcurrant ‘Titania’: robust and easy to care for; grows just about anywhere; large, deep black fruits that are slightly sour with typical blackcurrant aroma.
- Blackcurrant ‘Ben Connan’: small bush variety; Scottish bred; large black fruits with a superb flavour; heavy & early cropping from beginning of July; excellent mildew resistance; good frost tolerance.
- Blackcurrant ‘Big Ben’:bred in Scotland; crops early in the season; huge berries with an outstandingly delicious taste; bumper crop of up to 9kg; compact size.
How to grow blackcurrants
Growing blackcurrants is easy. They are undemanding shrubs that will thrive in almost any garden. Nevertheless, it is important to pay attention to where you plant your blackcurrant bush. Like their red and white counterparts, blackcurrant bushes grow naturally in forests. As such, they thrive in semi-shady locations, although most varieties can tolerate direct sunlight.
The right location for blackcurrants
Blackcurrants do not grow well with companion plants, so it is best to plant them alone. However, they do tolerate other currant species, including whitecurrants and redcurrants and also wormwood.
In fact, growing different varieties of currants together ensures that the flowers cross pollinate. It also helps prevent run-off, which occurs when individual berries fall off before they are ripe. Run-off results in a high loss of berries and a patchy currant vine.
Cassis flowers are sensitive to frost, so avoid planting them in draughty spots. Plant your blackcurrant bushes in moist, well-draining soil that is rich in humus. The soil does not need to be particularly deep, as blackcurrant bushes have wide-spreading, shallow root systems. They do not tolerate waterlogging, so if your soil is clayey, improve it before planting. Find out more about loosening compacted soil in our dedicated article.
To keep your blackcurrant’s shallow roots from drying out, add a layer of bark mulch, grass clippings or fresh compost to the ground around the plants, especially in the dry summer months. This not only keeps the soil from drying out, but also some mulch types add nutrients to the soil.
If you do not have a garden, you can also grow blackcurrant bushes in pots on a balcony or terrace. Just remember to use a large container, so that your plant’s wide-spreading root system can fully develop. A potassium-rich potting compost, like our Plantura Organic Tomato & Vegetable Compost is perfect for young, potted blackcurrant bushes.
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Planting blackcurrant bushes
Once you have found the right location for your blackcurrant plant, it is time to start planting! It is best to plant it in late autumn so that the first roots form before the growth phase begins in spring. That said, with sufficient watering, you can also plant a blackcurrant in early spring.
When planting new blackcurrant shrubs, space the plants 1 – 1.5m apart, as they tend to spread considerably. If you plan to cultivate rows of blackcurrant plants, space the rows 2.5 – 3m apart.
Plant blackcurrants in a hole at least 1.5 times the size of the root ball. The root ball should be about 5cm below the surface. This will promote adventitious root formation, i.e. roots that form on the stem, ensuring a dense and strong root system.
Mix the dug up soil with some fresh, nutrient-rich potting compost, such as our Plantura Organic Tomato & Vegetable Compost. This is a great time to work in some organic fertiliser granules or mature compost. Fill the planting hole with your soil mix and tread down well.
After planting, water your blackcurrant thoroughly. To make it easier to water your plant during its growth phase, create a ring around your shrub using excess soil. This ring ensures that water only seeps into the area directly around the blackcurrant bush.
Tip: standard-trained blackcurrant varieties will need to be permanently staked. To install a support, bury about a third of a bamboo cane into the ground, and tie the standard-trained blackcurrant to it at the stem, grafting point and central leading stem in the crown.
After planting, it is time to prune your blackcurrant plant. To prune a blackcurrant bush properly, choose five to six of the plant’s strongest stems and cut them back close to the ground so that just three to five buds remain. Then remove all other weaker shoots. Pruning blackcurrant bushes will ensure vigorous growth come spring and a solid structural support.
Summary: how to properly plant blackcurrant bushes
- When to plant: in late autumn or spring with constant watering
- Blackcurrant spacing: 1 – 1.5m between plants and 2.5 – 3m between rows
- Planting depth: 5cm deeper than the stem’s base
- Soil for blackcurrants: nutrient-rich, humus-rich, loose, well-draining soil
- Watering: regularly during dry periods; create a ring around the base
- Blackcurrant pruning: leave five to six main stems; shorten them so that three to five buds remain above the ground
Blackcurrant plant care
During hot summer months, it is very important to water shrubs regularly, as they are very sensitive to drought. Insufficient watering leads to harvest loss.
Fertilising black currant bushes
Blackcurrant plants need fertilising around two years after they are planted, as they tend to use up the soil’s nutrient reserves. For an abundant harvest, feed your blackcurrant plants at the beginning of February before they begin their vegetative growth phase. Use a long-lasting organic fertiliser, such as our Plantura All Purpose Plant Food. It is great for blackcurrants because it meets their potassium requirements.
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Pruning blackcurrant bushes properly
Annual blackcurrant pruning is essential for plant health and growth. When to prune blackcurrants? Immediately after the harvest so that it can put its energy into the remaining stems over winter and start the new year healthy.
Blackcurrant pruning is done to create a sparse bush. This way the sun can reach all parts of the plant equally. How to prune blackcurrants? Cut out thin, weak, diseased and troublesome branches, as well as those that are growing crosswise or lying on the ground. It is also important to remove all stems that are older than four years, as these older stems will not produce many blackcurrant fruits. This is a unique feature of blackcurrant plants that does not apply to redcurrant or whitecurrant shrubs. You can easily spot which branches to prune because young blackcurrant stems have a light, smooth surface that is clearly distinguishable from the darker, rougher older stems.
Blackcurrant diseases & pests
Blackcurrants are very robust and rarely suffer from disease. However, they can be susceptible to currant and gooseberry leaf spot (Drepanopeziza ribis), a fungal disease that causes spots on the leaves and eventually the leaves drop prematurely around July. To control currant and gooseberry leaf spot, rake up and dispose of infested leaves in autumn or winter to prevent the fungus from spreading as well as reinfection come spring.
Another fungal infection that tends to affect blackcurrant bushes is coral spot (Nectria cinnabarina). This fungus is easy to spot, it starts on dead wood as red spots but can quickly spread to live wood and cause the stems to die. To stop coral spot, generously prune out all infected parts of the plant and dispose of the cuttings.
Compared to other currant varieties, blackcurrants are much more susceptible to reversion virus, which is carried by the blackcurrant big bud mite, a gall mite in the family Eriophidae. If infection is caught early enough, prune back affected parts of the plant and dispose of in household waste. If the blackcurrant bush is badly affected, dig up and dispose of in household waste. Sadly, once it spreads too far, it cannot be reversed and can spread to other currant bushes nearby if not dealt with.
Pests can also infest blackcurrant plants. Aphids, scale insects, spider mites, gall mites, and lacewing aphids, are the most common blackcurrant pests. Various household remedies can help here. Spraying a stinging nettle decoction or a solution of 3% soft soap and 97% water on the pests is particularly effective.
Tip: blackcurrant run-off, which occurs when clusters of blackcurrants do not fully ripen, is often misinterpreted as disease. Run-off is caused by frost or a lack of pollinators. Planting a bee pasture near your blackcurrant bushes, which also supports our bees, is a great way to prevent run-off.
Propagating blackcurrants
Cuttings are the easiest way to propagate a blackcurrant bush. This method produces clones of the mother plant, so it is ideal if you enjoy the taste and yield of your blackcurrant variety.
To propagate blackcurrant plants using cuttings, choose a strong, healthy stem from your plant that is no more than two years old in spring and cut it off with clean, sharp secateurs. Cut the stem at angle into one or more 20cm sections, making sure each piece has two to three buds. Cutting the stem at an angle also helps to prevent water from sitting on top of the blackcurrant cutting and fungal infections. Finally, put these cuttings into pots filled with seedling compost, leaving at least two buds protruding from the soil. Water regularly and wait!
Harvesting & using blackcurrants
Blackcurrants ripen later than redcurrants. When to harvest blackcurrants? From mid-to-late July until late August. Blackcurrant fruits are extremely healthy and can be eaten raw, added to fruit salads or simply enjoyed on their own. Unprocessed blackcurrants are high in vitamins, especially vitamin C, as well as tannins and minerals. Nevertheless, only eat raw blackcurrant berries when they are fully ripe. If necessary, you can freeze blackcurrants for later use.
You can also make blackcurrants into jam, liqueur, or add them to cakes. They are delicious in smoothies as well as in savoury sauces. Blackcurrant leaves can be used in an unusual way. That is, blackcurrant leaves can be made into a vegetable soup that is especially nutritious, as they contain flavonoids, essential oils and anthocyanins.
