Growing Cold-Hardy Currants
Nov 7th, 2011 | By Esther | Category: Food, Gardening | Print This Article
Currants are a fast growing, deciduous shrub, which produce multiple stems that can grow five feet wide and high. Most currants are self fertile, but some cultivars are partially self-sterile, so planting them in twos and threes is a good for producing more fruit. Currants are hardy in zones 3 through 5, but they adapt well to containers in other areas.
Currants prefer morning sun and partial shade in the afternoons with plenty of air circulation. They prefer cool heavy soils that are rich in clay and have good moisture retention. Sandy soil dries out to quickly, which can cause soil to overheat. (A thick mulch of organic matter keeps soil cool in summer and adds nutrients too.) The plants tend to collapse when soil or air exceeds 85 degrees. They prefer a slightly acidic pH of 5.5 – 7.0 and do not tolerate alkaline or salty soils.
Leaves alternate maple-like and single-lobed versions. Black varieties have pale green leaves, while red currant leaves are deep blue-green. Both are easily sunburned by intense sunlight. Leaves tend to be smaller and fewer when water is scarce.
Currant flowers grow toward the base of one-year-old stems and on the twiggy branches of older ones. Each bud opens to a cluster of blossoms – up to twenty – joined together on delicate, drooping five-to-six inch “strigs.” Strig length is reduced and flowering suppressed by a lack of winter chill. Red currants have greenish flowers while the black cultivars produce a blush-pink flower. While individual flowers are not showy, the joined clusters give the bush a lace-like texture. To increase number and size of berries, clip off a bit of the strig end while they are flowering. Insects pollinate currants, and berries will ripen in seventy to one hundred days.
Fully set strigs will form pendulous chains of berries. They pick easily when strigs have long “handles” (clear lengths at their bases) to hold while harvesting. Black currants ripen from the top down encouraging birds to strip berries as they color while red, white, and pink berries tend to ripen all at once on each strig. Black currants are a matte brown-purple, while red, white, and pink currants are translucent; all contain three to twelve bony, minute seeds.
Irrigation: Currants have shallow, fibrous root systems and are good candidates for drip systems. Water berries well until harvested, then reduce watering frequency. Do not quit watering altogether, as this stresses plants and makes them susceptible to mildew.
Fertilizing: Apply nitrogen to your currants at a rate of about four ounces per square yard, but remember that using too much will cause the bushes to be disease prone. Amending with compost will add organic nitrogen. There are other forms available too. If potassium deficient, they will have marginal leaf scorching. Adding ½ ounce potassium per square yard will prevent this. Avoid using potassium chloride, as currants are sensitive to the chloride ion.
Pruning: Pruning annually increases yield while maintaining plant manageability. Prune so most of the fruit are on the spurs of two-to-three-year-old wood. The first winter you will remove all but two or three stems to ground level. Continue this until the fourth winter, when you should cut away all stems more than three years old. Also trim back all stems that are long and scraggly. Pruning is best in the new moon; this is when sap is lowest in the plants. Also, do not prune once spring growth has begun.
Propagating: Currant seeds will germinate if stratified (placing them between layers of earth) for three to four months at about thirty degrees. Bushes grown from these seedlings will bear fruit in the second or third year. Currants can also be propagated by taking cuttings of one-year-old wood. Make cuttings a foot long when plants are dormant in late winter. Dip the base of cuttings in rooting hormone and pot in ordinary soil, stripping all buds off that will be below the soil line. Cuttings will root quickly and should be kept in the shade the first year.
Diseases and Pests: Gall mites infest dormant buds in summer. Buds swell, form dry rosettes, and fail to break during the next spring. Whole stems become blind and die back to the ground. Upon detection the plant should be immediately removed and burned. Aphids commonly distort the foliage, causing red spots. Spider mites are common and also cause foliage distortion. Clear-winged borers lay eggs on stems in late spring. Larvae hatch and bore into stems, remaining until next season. Infestations are usually detected when stems wilt and die. Borers will spread, causing loss of a whole planting without eradication. Cut out affected stems. Search for other bulges and eggs and spray with a natural pesticide.
In black currants (rarely in red) the most feared disease is revision virus. It appears as weak barren plants with pleated leaves and is spread by gall and common mites. This is endemic in Europe, but not known in the U.S. There is no cure, so do not order any plants from Europe. Ribes species are host to white pine blister rust. This causes few problems to currants but is lethal for five-needle pines like Western White Pine and Sugar Pine. Currants are banned in counties where these pine varieties are grown for lumber. Botrytis and Anthracnose cause leaf rot and loss of young growth, usually on stems lying on the ground or splashed during irrigation. Gooseberry mildew will infect currants, especially in humid places. It is worse in areas where fog is common and where irrigation is by overhead sprinkling. Keep plants turgid, never water-stressed. Spraying a broad spectrum, organic fungicide on the plants before they flower and after harvesting should control this mildew. Currant roots are susceptible to Oak Root fungus (Amillaria) and Phytophthora. Check with the Agricultural Extension Office in your area to see if they are common and how best to treat them.
Harvesting: Most cultivars hold onto berries well. When eating berries fresh, let them hang on the bush about three weeks after reaching full color. If they are to be stored, pick dry. To avoid damage, pick the whole strig by the stem, being careful not to damage the spur. Yields will vary by cultivar and growing conditions. A single bush can produce from three to over ten pounds. Currants are known for their use in jellies but are also tasty in pies and sauce. They also make wines that compare to Graves or Rhine wines.
Red Currants – Best for juices, jellies, and purees. Selected for clarity of juice, size of berries, and productivity.
- Jonkheer van Tets
- Red Lake
White Currants – An albino form of red currants. More versatile and less colorful, but fine for culinary purposes. Less acidic, which makes them good for fresh eating. The best are nearly transparent.
- Weisse aus Juterbog
- White Imperial
- White Versailles
Pink Currants – An intermediate between red and white varieties in degree of pigmentation. Skin is colorless while the flesh is pink.
- Gloire des Sablons – an ancient variety from France.
Black Currants – Characteristic aroma will emanate from leaves when rubbed. Highly esteemed by those from northern Europe. Astringent, suitable for culinary purposes only.
- Boskoop Giant
- Noir de Bourgogne
- Wellington XXX
Good luck planting your currants! Enjoy!
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