Keeping up with currant affairs
Black and red currants (Ribes species) are indigenous to the colder parts of the northern hemisphere where they have been harvested for centuries. They are very high in vitamin C, more than four times the amount found in citrus fruits, and significant quantities of vitamin E.
Currants need to be grown in an open site, but do well where they do not receive too much hot afternoon heat. They need to be sheltered from drying winds and too much salty air damages the leaves. Currants do best in cool, moist conditions and should never be allowed to dry out. They need a definite winter chill to produce flowers and leaves, so they do well in Nelson with its clearly defined seasons, unlike the far north.
Being termed ‘‘gross feeders’’ all currants do best in a compost -enriched slightly heavy soil that retains the moisture the plants need to produce heavy crops and plenty of new growth for next season’s fruit production.
However, they do not like soils which are waterlogged and do best in thosewhich have a slightly acidic pH reaction. They can be given a dose of citrus fertiliser in early spring and then mulched to retain moisture.
Both red and black currants are susceptible to potash deficiency, so it is recommended to incorporate about 30 grams of sulphate of potash per square metre.
Currants need to be pruned to encourage the new wood on which they fruit the following season. Fruiting canes should be kept to about eight per bush and old three year wood should be removed. New fresh canes will appear from the base of these the next spring.
If you have the room you can grow two rows of currants and cut them back to just above the ground in alternate years.
The main pest of currants is the Currant Clearwing moth (Synanthedon tipuliformis)
which lays its eggs on the buds and canes. When the larvae hatch they burrow into the stem to feed, weakening the canes and reducing plant food reserves, which lessens the yield and quality of the fruit.
Unfortunately this pest is around at the time the fruit is developing so spraying is not an ideal solution. Keeping the bushes free of old infected wood by pruning is the best solution.
Growing enough bushes so that you can chop half of them down in alternate years is a good control. Remember to burn old infected wood.
Black currant production in New Zealand is the highest out- side of Europe with about 8000 tonnes annually, about 4% of world production. Breeding programs are tailored to producing high yield varieties with high concentrations of compounds known to be beneficial to human health.
Currants freeze well and can be taken out to make delicious pies, jams or turned into cordial for very healthy drinks.