GROWING CURRANTS

A currant is a sweet, or tart, or musky heavy tasting edible fruit produced by a currant bush (Ribes species). Currant bushes are grown worldwide, preferring cooler summers to hot ones, and have been cultivated by humans for hundreds of years. There are several named varieties and colors of currant, so it is important to choose one that is right for your area and preference. Red currants are eaten fresh, used for jams and jellies, or can be mixed with applesauce to make butters or leathers. Their flavor tends to be sweet tart. Black currants are less likely to be eaten fresh, and more likely to be used for jams and jellies, butters and fruit leathers, drying, and liqueurs. Their flavor is sweet tart, heavier than red currants, and sometimes musky. White and pink currants are used for fresh eating, and jams and jellies, sometimes also butters and leathers. Their flavor tends to be milder and sweeter than red currants.

CHOOSING A VARIETY

SIZE

Currant bushes are best maintained at 3-5‘ tall and 3-5 ‘ wide. If allowed to exceed 5’ they tend to start flopping over.

POLLINATION

Some black currants are not self-fertile and require another black currant as a pollenizer to produce fruit.

Red, white, and pink currants are self-fertile, so do not require a different variety as a pollenizer to produce fruit.

The pollenizers should be planted no further than pollen carrying bees will fly, with no line of sight obstruction, to ensure proper cross-pollination. That distance varies with different bees, 100’ should be a good average distance.

RIPENING TIME

Fruit ripen late spring to late summer depending on variety and location.

USDA HARDINESS ZONE

Currants are hardy to USDA zones 3-8. This rating tells you the minimum winter temperature the plants typically survive when properly hardened off. On our web site you will find a USDA Hardiness Maps which provides information on the average minimum winter temperature in your location, by zip code.

CHILL HOURS

Many plants native to locations that have cold winters have a Chill Hour requirement to ensure uniform waking up of flower and leaf buds in the spring. The chill hour requirement of plants varies by species, by cultivar, and sometimes by the level of dormancy achieved.

WHERE TO PLANT YOUR TREE

Currants need to be planted where they receive at least 8 hours of direct sunlight measured in early summer (late June to early August), and afternoon shade in hot dry summer locations. Sufficient sun exposure triggers the initiation of new flower buds for the next growing season, without which there will be no fruit. Fruit ripening and flavor development are also benefited by the carbohydrate production stimulated by the sun, as well as it’s heat.

Currants tolerate a wide variety of soils so long as they are well drained and moderately rich with a pH around 5-7. Improve your soil where you intend to plant by mixing an inch or two of plant based organic matter (manures are best for vegetable gardens), peat, or coconut coir into an area 1 1/2 to 2 times the diameter of the needed planting hole and up to a foot deep. A 2-4” deep layer of mulch (straw, leaves, or wood chips) applied after planting will continue to improve the soil.

Allow sufficient space for both the top of the tree and it’s roots when selecting the planting location. Refer to size descriptions for each variety, keeping in mind these are generally managed or pruned sizes, not maximum potential sizes. If you are planting an orchard be sure to include enough space between rows for transporting supplies in and fruit out.

GROWING IN CONTAINERS

To grow a currant bush in a pot you need a final container size of at least 10 gallons. Bushes will grow larger in a larger container, but make sure you have the ability and tools to move the pots heavy weight. It is important for the establishment of the root system to gradually increase the size of the container over several years, rather than go from small directly to very large.

Do not use soil from your garden in the pot, instead use a potting soil mix with some added compost. For larger pots use a potting mix that has larger particles in addition to the smaller.

CARE AND MAINTENANCE

WATERING YOUR TREE

This is the most important and often the most difficult part of successfully growing plants. There are many factors, including the humidity, temperature, soil type, wind, and amount of direct sun that affect how much and how often water should be applied.

A general rule of thumb for plants in the ground is to ensure they receive an inch of water per week over the root zone. An inch of water is equivalent to about ¾ to one gallon per square foot of soil surface area. The typical three foot diameter planting hole would need 7 ½ to 10 gallons of water per week provided by rainfall or by the gardener.

Apply this water once a week, two times per week if soil is fast draining. This will of course depend on your own conditions and the plants you are growing! DO NOT waterlightly each day because this results in a wet surface and dry root zone area. The soil should be moist but not soggy to a depth of about a foot for most growing plants. The top inch or two can feel dry, and the plant still be well watered. The trick is to have the water available where the roots are. In hotter and sunnier areas, a mulch of straw, bark, etc. can greatly ease the burden of summer watering. For plants in containers, water until the soil is saturated and water comes out of the drainage holes. Let the container dry until the soil is dry to the touch 1-2 inches down (more deep with deeper pots) and the container is lighter in weight. A plant that has wilted canbe receiving either too much or too little water.

In rainy areas like the Pacific Northwest most of the plants that we offer will need relatively little supplemental irrigation ONCE THEY ARE WELL ESTABLISHED in the ground and have had a chance to develop a good root system. However even here it is important to make sure plants have regular, deep watering during the first couple of growing seasons, and the first summer is especially critical. In drier areas, or where soils do not retain water well, permanent irrigation is essential. Remember that you don’t want your trees to just survive, but rather to thrive. Make sure they get the water where they need it, starting at the drip line and extending away from the tree up to several feet ( for older trees) where the feeder roots will be. Drip irrigation and soaker hoses can be an efficient way to deliver the water.

FERTILIZATION

For good steady growth and high productivity, your trees need to have adequate amounts of various mineral nutrients. Some people are fortunate and have naturally rich fertile soil.

Use an all-purpose or balanced fertilizer. A couple of inches of well-rotted compost on the root zone can also be an effective fertilizer. A generous leaf or straw mulch around your trees will not only conserve moisture and help in weed control, but also keeps your soil healthy by building up humus, attracting earthworms, and supporting beneficial fungal organisms. This encourages young trees to be strong, healthy and productive. Avoid applying fertilizer after early summer, doing so can encourage lots of soft new growth that is much more likely to be damaged by winter cold. Excessive use of fertilizer can in-crease disease problems on your plants and can even kill them.

As a general guide, if your tree is producing about one foot of new growth or more a year and has healthy looking foliage, it may not need much or any fertilizer.

PESTS AND DISEASES

Find out what insects and diseases are typical in your area. Ask your local co-operative extension professional what the typical insect and disease issues are in your area. Then you can make selections based on resistance or tolerance information available in our catalog, or, make a plan for controlling problems you can expect with the susceptible varieties you prefer to grow. If you see resistance information about a particular disease for one variety but not another of the same kind of fruit, then that variety may be susceptible or might not have been tested so is unknown. The following are some of the more common issues.

ANTHRACNOSE LEAF SPOT

SYMPTOMS - Leaves get brown spots, turn yellow, then fall off.

CONTROL METHODS - Copper fungicide applied in fall, winter, or spring. Prune out weak or injured wood.

COMMENTS - Rake leaves from under plants in fall.

WHITE PINE BLISTER RUST

SYMPTOMS - Extensive reddish colored blisters on black current leaves. Defoliation often occurs in bad infections.

CONTROL METHODS - Spray copper fungicide in fall before rains. Repeat in early spring.

COMMENTS - Black and flowering currants tend to be more susceptible than red and white. Do not plant within 900’ of white or 5-needled pines.

IMPORTED CURRANT WORM

SYMPTOMS - Leaves eaten, starting at the lower part of the bush and proceeding up and out. Small green caterpillars line chewed leaf edge. Can appear to be defoliated almost overnight.

CONTROL METHODS - Spray with pyrethrin or rotenone, at first discovery of the little green caterpillars, and subsequent generations through summer. Search daily and destroy by hand. Cover with floating row cover.

COMMENTS - Ducks find new caterpillars easily. Use Bioneem or Spinosad.

CURRANT FRUIT FLY

SYMPTOMS - Infested fruits filled with tunneling maggots, ripen and fall prematurely.

CONTROL METHODS - Spray with rotenone at petal fall. Or use spinosad or bioneem. Pick up and discard affected fruit. Protect bush with floating row cover during fruiting, but tie so pests can’t come up from below. Shallow cultivation under bushes to expose egg cases and larvae to predators can reduce populations.

COMMENTS - Plastic mulches when fruit is ripening can help prevent larvae from entering the soil.

SPOTTED WING DROSOPHILA

SYMPTOMS - Eggs are deposited 7-10 days prior to fruit ripening; holes in fruit, spotty molding, larvae in fruit, exuding berry sap, scarring.

CONTROL METHODS - Monitor with traps. Spinosyn based insecticides. Sanitation: In fall, adults feed on over ripe or split fruit (both vegetable and tree fruit) to prepare for winter.

COMMENTS - Go to https://agsci.oregonstate.edu/spotted-wing-drosophila/what-backyard-fruit-growers-need-know-about-swd-drosophila-suzukii-fly-pest for current information, or check with your local co-operative extension office.

DEER

SYMPTOMS - Browsed shortened branches. Leaves are obviously munched on or plants are pulled up.

CONTROL METHODS - Fences or cages at least 8’ tall. Plastic mesh, electric, or woven wire fences.

COMMENTS - At Raintree, an 8’ woven wire deer fence has worked best. Repellents don’t work consistently. and only trained large dogs patrolling the perimeter are effective. Some have had success with the product “Deerchaser.”

BIRD

SYMPTOMS - Fruits disappear or have gaping holes in them. Strawberries, blueberries, cherries and filberts are most susceptible but most fruits suffer occasionally.

CONTROL METHODS - Reflective Bird Scare Tape can work well. Bird netting. Cages.

COMMENTS - Blue Jays start harvesting filberts when ready to pick, and so should you. Nuts dropped by jays are usually empty.

VOLE/MOUSE/RABBIT

SYMPTOMS - Bark eaten in a band from soil level up to 8” and roots eaten too, usually in snowy areas with lots of mulch or tall grass at base of trees.

CONTROL METHODS - Keep mulch 4”-6” away from trunk. Keep grass short and 1’-2’ from trunk. Use vinyl tree guard wrapped around trunk until tree well-established.

COMMENTS - Voles and mice will chew a couple inches above ground and also into the root system. Rabbits will chew up to 8” high, particularly apple trees.

APHID

SYMPTOMS - 1/32 to 1/8” long pear shaped insects that multiply rapidly, espe- cially on the underside of leaves and on stems. Can be pink, green, black or white. Leaves show red blisters or are curled-down and stems turn black with sooty mold.

CONTROL METHODS - Natural predators like lady bugs and parasitic wasps often provide control. Knock aphids off with water spray. Spray with Pyrethrin, Rotenone, Insecticidal Soap, or delayed dormant oil. Control ants if they are also present.

COMMENTS - Trees can tolerate some infestation. Monitor in late spring and summer. Control is more important on new trees. Grow plants that attract predators, i.e. dill or yarrow.

ANT

SYMPTOMS - Numerous ants scurrying up and down the tree trunk; aphids, scale or mealybug present in large numbers, lots of sticky honeydew, perhaps sooty mold.

CONTROL METHODS - Find hill and apply pesticide. Apply Tangle Trap over 2-3” wide band of paper wrapped around trunk. Eliminate other pathways into tree.

COMMENTS - Ants nurture and protect these insects in exchange for their sugary secretions. Insects may be difficult to control until the ants are controlled.

BROWN MARMORATED STINK BUG

SYMPTOMS - Poking-type feeding damage followed by decay on fruits, nuts, berries and leaves. Deformity in the healthy tissue surrounding the dead tissue. Brown spots can show up in stored fruit.

CONTROL METHODS - Monitor with traps, some broad spectrum pesticides may work. Researchers are working on finding effective controls, but no info has been released yet.

COMMENTS - BMSB over winters in groups in dry protected areas, such as houses. If you find them on or in your home use the vacuum, squishing releases their defensive stink. See stopbmsb.org for more info. Feeding begins in spring when the weather warms up and continues until new adults go dormant for winter.