Blackcurrants fruits

Blackcurrants – love ‘em or hate ‘em. Once a Kiwi backyard staple and famed for their legendary vitamin C content, these tiny purple pearls seemed to wane in popularity a few decades back as newer, sweeter berry cultivars arrived on the scene. However, this pungent but humble fruit has recently enjoyed renewed interest after research conducted right here in Aotearoa pushed it into the limelight as the poster child for post-exercise recovery and brain-boosting benefits. Even if you’re just a fan of their tart, herbaceous flavour (less so their ability to stain anything within a hundred-metre radius of a vivid, vibrant purple) they make an easy-care, versatile crop for the home garden.

If you’ve grown or known currants in the past, you’ll know that if you brush up against the foliage the leaves release a strong, unmistakeable curranty odour. If you find this pleasant, as many do, you’ll be pleased to know that blackcurrant leaves can be used as a flavouring agent in their own right. They make a fantastically aromatic herbal tea and cordial (move over, Ribena) and are also used to lend a distinctive flavour, much as you would use bay leaves, in all manner of sweet and savoury dishes – think ice cream, custard and pickled cucumbers or gherkins for starters.

Blackcurrants are cold-hardy and prolific, with the fruit ripening about now in mid-December through January. Often overshadowed by the sweeter and far showier berries available at this time, it’s certainly worth making space for a couple of bushes in the garden for a ready supply of fruit for cooked desserts, cordials and preserves – and if you have a strong constitution, perhaps even as a dessert fruit.

 

Red and white currants: a short family history

Currants belong to the Grossulariaceae (the gooseberry family – currants and gooseberries are cousins) and more specifically to the genus Ribes. Blackcurrants are domesticated varieties of their wild ancestor, Ribes nigrum, which is native to Europe and Central and Northern Asia, including Siberia.  

Blackcurrants appeared on the scene in British gardens in the 1700s, sometime after their much more favoured at the time red and white cousins. The fruit was given the name ‘currant’ in recognition of its superficial resemblance to the small dried fruit produced from grapes, the name of which is itself derived from Corinth, a city in Greece well known for its grape production over the centuries. The blackcurrant’s pungent foliage and robustly-flavoured berries seem to sadly contribute to this fruit being consigned largely to medicinal purposes, although its high vitamin C content has always been held in high regard. During the Second World War, in the absence of oranges, every schoolchild in Britain received a free supply of locally-produced blackcurrant juice, with the fruit thriving in the region’s cool climate.   

Over in North America however, less than 0.1% of the population has ever tried a blackcurrant. Although cultivated blackcurrants travelled to the USA with British migrants in the 1600s and were grown on a reasonably large scale for some time, that all changed in the early 20th century when blackcurrants were found to be a host of white pine blister rust (Cronartium ribicola) (WPBR), for which there was no remedy at the time. With the plants posing a huge risk to the burgeoning timber industry (white pine being a keystone species), the federal government banned the propagation, cultivation, sale and transport of blackcurrant plants. 

The most WPBR-susceptible Ribes varieties were found to be blackcurrant species, so existing areas under cultivation were obliterated by spraying, effectively eliminating the fruit from the country.  Native North American currant species (a component of natural forest understories) appear to have escaped (or at least survived) this extermination period, due to being less-suitable hosts for the fungus. With the advent of rust-resistant currant cultivars, the ban on currant cultivation was lifted in 1966, but to this day some states retain some degree of restriction, meaning in some areas even backyard growers need to obtain permission from local authorities to grow the fruit at home – for example, cultivation in New York state has only been allowed since 2003. 

 

Suitable climates and growing conditions

Due to their cool-climate Northern Hemisphere origins, blackcurrants thrive in colder areas, where hard winter frosts provide the 800 to 1500 hours of winter chill required for the bushes to set fruit. They grow well throughout the South Island and lower North Island. Fruit set is reduced where winter chill is insufficient, hence growers in the Far North may struggle. Blackcurrant buds begin to move quickly towards the end of winter, so there may be the danger of damage to young foliage and flowers in regions prone to late frosts. Cool, humid summers are ideal for the Ribes ripening phase, which is why much of New Zealand’s commercial blackcurrant cultivation is focused on the southern districts. They even grow well on the West Coast of the South Island, where other fruit crops may struggle to ripen.    

 

Site selection and planting

Currants are one of the few fruiting plants which thrive in partial shade – great for areas where other fruit crops would sulk. A sheltered position, open to the morning sun but shielded from the heat of the afternoon is ideal. In my family’s orchard, blackcurrants grow and produce happily in the shade of several mature apple trees. You could also utilise the south side of a shed or other garden structure to provide respite from the afternoon sun. Aim to leave 1.5 to two metres between plants. You can expect mature plants to attain a height and spread of around two metres or more in either direction.   

Blackcurrants are tolerant of a wide range of soil conditions, including heavier clays in which other soft fruit crops fruit will turn up their toes, but well-drained, fertile types are best. They will not tolerate waterlogging. Plant blackcurrant bushes in autumn (May is ideal) and no later than August, as the new season’s growth commences early in spring.       

 

Culture and care

Blackcurrant bushes are shallow-rooted, so watering is key at certain growth stages. Avoid cultivating close to the plants and disturbing the roots – blackcurrants are particularly sensitive to having their roots disturbed during flowering. Keep plants well-watered, especially when grown on sandier soil types, but avoid overwatering. The plants flower in early spring and are insect-pollinated. Keep the water up from flowering right through the fruit development stages to harvest, which is usually from mid-December to January. After harvest, water requirements decrease. A layer of organic mulch will help retain soil moisture and keep the plant’s shallow roots cool in the height of summer.   

Blackcurrants are not gross feeders, so a single application of general fertiliser in the spring is sufficient for year-round maintenance. Allow 350 g for a mature plant (around three or more years of age), and reduce this amount proportionally in the establishment phase and early years by taking the age and size of your plants into account. Apply before forecast rainfall, or hand-water in well after spreading – aim to cover a square metre with every cupful of fertiliser.

The patient can grow currants from seed - I’ve seen literal lawns of young plants coming away in the understorey beneath commercial plantings! For reliability, choose clonally propagated nursery-grown plants of known cultivars. If you know someone with a fantastic variety in their garden, propagation from cuttings is super simple and the strike rate is high. We have some very old, un-named large-fruited blackcurrants in our garden which we saved from an elderly gentleman’s property before it went under the bulldozer and I try to re-propagate these now and again to maintain vigour and just in case we ever lose the original plants to old age. Cut 20-30 cm lengths of either semi-hard wood in autumn, or dormant hardwood in winter. These can be planted directly into the ground where you wish the plants to grow, or into pots – currants produce roots so readily there is even no particular need to use a specialist propagation mix or a rooting hormone, but neither of these will do any harm. Bury two-thirds of each cutting in the growing media, leaving just two or three buds above ground.   

Mature bushes will produce around 4.5 kg of fruit, which is best harvested by picking whole sprays of fruit with the stem intact. They freeze beautifully. Use the tines of a fork to zip the strings of jewel-like currants off their stems. If you are finicky, you can also do what my Mum does and ‘top and tail’ the currants before cooking or freezing. This involves removing the papery calyces and any stem remnants by trimming them off with a small sharp knife. I’m far too impatient (read: lazy), but superior results require dedication to the cause! Plants will remain productive for 10-15 years if well-maintained.

 

Pruning

Blackcurrants fruit on one-year-old wood, so don’t expect a crop in the first year after planting. Blackcurrant branches arise directly from the ground, unlike red and white currants, which have a short trunk. It’s good to aim for bushes with an open centre, which will allow for light penetration (even ripening) and good airflow through the canopy (for disease prevention). When removing wood, cut stems right back at the base of the plant to a low, outward-facing bud if you’re not removing them completely. You can keep some two-year-old wood if necessary, but wood three years or older really should go.

Some people prune their blackcurrants soon after harvest, using the current season’s fruit stalks as an identifier of what needs to go. Eventually, you’ll be able to distinguish the darker two-plus-year-old wood from one-year-old fruiting wood and the current season’s new growth. Blackcurrants need a decent prune each year to encourage the growth of new shoots from the base of the plant, which will fruit the following year. You may end up removing up to a third of each bush, probably a bit more from very old plants. Commercial growers sometimes take the concept of rejuvenation very seriously, pruning off old bushes at ground level to encourage them to re-sprout. As with all winter-dormant deciduous fruiting plants, aim to complete your pruning before the new spring growth begins.          

 

Pests, diseases and what to do about them

The number one blackcurrant pest (apart from greedy birds) is the currant clearwing moth (Synanthedon tipuliformis). The adult moths are an ornate wonder of nature, truly a sight to behold and look more like an ornate fly than a moth. Sadly, their offspring are bad, bad news for your blackcurrant crop. The adult moths lay eggs on the canes during spring and summer, which then hatch and the larvae bore into the shoots, tunnelling them out. Unchecked, they are capable of destroying the whole bush. If you notice any damage, usually indicated by dieback or unhealthy-looking branches, cut some stems open – if you see hollow, black centres instead of healthy green-white piths, you have resident currant clearwing larvae. Prune the infested shoots back to healthy material, seal with pruning paint and burn the affected material immediately. Commercial growers use pheromone ties to disrupt the adults’ mating cycle.

Other pests present in New Zealand that can have a detrimental effect on currants in New Zealand are blackcurrant gall mites (Cecidophyopsis ribis), scale insects, two-spotted mites, leafrollers and the lettuce-currant aphid, Nasonovia ribisnigri. 

Fungal pathogens include cane dieback caused by Botryosphaeria ribis, and flower blight and leaf rot by Botrytis cinerea. Gooseberry mildew (Podosphaera mors-uvae) can also be a problem, especially in humid climates. The home gardener’s best defence against fungal disease is to maintain an open canopy with good airflow and avoid overwatering.  

Keep a watch for flowering currant (Ribes sanguineum). This less-welcome currant has broad, hairy currant-esque leaves, bright pink flowers and a strong, musky currant-like scent. It’s highly conspicuous in later winter-early spring (you’ll probably smell it before you see it) and is a prolific seeder and coloniser along waterways, on dry rocky slopes, in shrubland, forest gaps and bush clearings, posing a threat to the native species it is so good at displacing. 

 

Varieties: My top picks

There are several New Zealand-bred blackcurrant cultivars in existence but most are only available to licensed growers for commercial purposes. Many of the cultivars available to home growers in New Zealand are from the Scottish Crop Research Institute’s ‘Ben’ series. SCRI (now the James Hutton Institute) began breeding blackcurrants in 1956 and became home to one of the world’s largest blackcurrant breeding programmes, as the fruit thrives in the cool northern climate. Climate change brings new challenges, along with it the need for new cultivars that produce well with reduced winter chilling hours.

Magnus – Historically New Zealand’s main commercial variety and widely available, which is why I’ve included it here. Hardy, produces large black fruit mid-season (late December to January). 

Ben Mapua – High-yielding, late-season, large-size fruit is produced about two weeks after Magnus in February. Vigorous, spreading plants.

Bed Ard – Needs reasonable winter chill, but slightly less than Magnus. Suited to the south of the South Island. High levels of antioxidants. Ripe late December to early February.

Ben Rua – Slightly lower chill requirements, can be finicky to grow, large low-acid berries produced late December to February. 

Sefton – Requires less chilling hours than Magnus, fruit ripens mid-late season (late December to early February). Sweeter than most other cultivars.

Keen on something slightly different?  

Look out for the Worcesterberry, Ribes divaricatum, probably a blackcurrant-gooseberry hybrid. The fruit is smaller than a gooseberry but larger than a blackcurrant and the plants can be shy producers. They have unfortunately inherited thorns from their gooseberry relatives. Extremely cold-hardy.

What to do with your crop

In my opinion, blackcurrants are at their best cooked in dessert form, so make sure you freeze a plentiful stash for the colder days in winter. Try them lightly stewed, sweetened to taste (honey makes a nice change from sugar) and thickened with a little tapioca or cornflour as a pie, cobbler or crumble filling. For the latter, try mixing with some stewed apple to soften the flavour if serving to younger palates or picky eaters.

You can make cordial and either bottle or freeze it for long storage. Substitute frozen blackcurrants cup for cup in cake and muffin recipes for a flavour and antioxidant boost. Cross the sweet-savoury divide, get the vinegar out and try making a blackcurrant vinegar to sharpen winter salads, or a blackcurrant sauce for serving with game meats. Digby Law’s legendary Pickle and Chutney Cookbook has suggestions for both. 

If you preserve your gherkins, add a blackcurrant leaf or two to the bottom of each jar along with your regular spices for a twist on tradition. If you ferment rather than pickle, you could add some leaves to your brine – apparently, the tannins contained in the leaves help keep pickles crisp, as well as add to the overall flavour profile.

Blackcurrants blend well with chocolate, liquorice and vanilla. I’ve tried dehydrating the berries whole (not recommended, takes forever unless you break the skin somehow, and I still had to finish them off in the oven) but the small quantity I did manage to get to a dry state was blended with black tea leaves and shredded vanilla pods to create a pretty pleasant brew. A good friend rates blackcurrants as her favourite fruit to add to her kombucha-brewing vessel at the secondary ferment stage. 
When I find a spare moment this summer, I plan to try this recipe for blackcurrant leaf cordial: https://myvintagecooking.com/homemade-blackcurrant-leaf-juice/

If you’re a keen ice cream or sorbet maker, infuse a few handfuls of blackcurrant leaves in the warm liquid component of your next batch – I think this would work well for custards too, much in the same way people will use a peach or bay leaf. A good ratio seems to be 25 leaves for every 300 ml liquid, infuse for an hour then remove. Happy experimenting!


Anna-Marie Barnes is an active member of the New Zealand Tree Crops Association who endeavours to grow and preserve as much of her fresh produce as possible. When the weather’s no good for gardening, she can usually be found inside working on a batch of homemade cheese or soap.

The New Zealand Tree Crops Association is a voluntary organisation promoting interest in useful trees, such as those producing fruit, nuts, timber, fuel, wood, stock fodder, bee forage and other productive crops. Find out more about the NZTCA here: https://treecrops.org.nz/

Disclaimer: The information supplied above is general and provided as reference material only. In regards to pest and disease control, please consult your agrichemical consultant for suitable products, application rates and further region-specific information.

Image credits

Blackcurrant fruit - Images by PublicDomainPicture via pixabay.com

Blackcurrant buds - Image by mrninko via pixabay.com

Blackcurrant green fruit and foliage – Anna-Marie Barnes