Wait to Prune Raspberries
By Roberta Bailey
Raspberries are the most commonly grown bramble in the home garden. For those preparing to make the leap out of the tomato patch and go beyond cucumbers, raspberries are an easy choice: You can be eating freshly picked berries in just a few years.
Depending on the variety, raspberries supply a summer or fall harvest. They also provide fruit of several flavors and colors. Rubus idaeus includes the red and gold species, R. occidentalis, the black raspberry, and R. neglectus the purple raspberries, which are a cross between red and black raspberries.
Raspberry roots are perennial while their canes are biennial. In their first year of growth, they put forth vegetative canes called primocanes, which form flowering buds late in the season. The next year these canes, now called floricanes, become productive and bear fruit, while the plant is also producing new primocanes for next year’s harvest. After fruiting, the floricanes die and can be removed.
Brambles are fairly shallow rooted plants, with 90 percent of their roots found in the top 2 feet of soil. A rich soil, free of weed competition, is imperative for productive, long-lived plants. Choose a site with good air drainage but with some protection from drying winter winds. Well drained loams or sandy loams are ideal. Raspberries do not like wet roots or droughty soils. Mulch and irrigation can help overcome dry conditions, but standing water or continually wet roots invite rot. As raspberries send out lateral roots for 2 to 4 feet, choose a site where you can contain their spreading habit.
In preparing a site, planting weed smothering cover crops the previous year is ideal. Prepare your soil as thoroughly as you would for a vegetable garden. Add lots of compost (15 lbs. dried or 10 bu. fresh per 100 sq. ft.), working it into the top 4 feet of soil. If possible, select a site 400 to 600 yards from neighboring or wild raspberries that may harbor disease. Brambles grow best in a soil of pH 6.0 to 7.0.
The size of your patch will depend on your needs. Do you want to freeze berries, make jam, sell the fruits, or just have a few for breakfast? On average, each foot of row bears one pint of berries. A household of four planning to put up some berries should start with 50 plants, which should yield 80 to 100 pints of berries.
A raspberry patch is said to live for 10 years. I know people who have maintained a very productive patch for over 30 years. I suspect that the care and feeding given them affects longevity.
Raspberries are considered hardy in USDA zones three through eight. In Maine, it is important to select varieties that are truly hardy. Most red and yellow cultivars are hardy into Canada. Black and purple raspberries are slightly less hardy (see listing below).
Select disease and virus-free plants from a reputable nursery. Gift plants from a neighbor often give you more disease trouble than fruit.
Plant raspberries as early in the spring as the ground can be worked. Preparing the bed the previous fall makes this an easy task. Plants often come bare-root. Open the package and soak the roots for a few hours before planting. Set raspberries 2 to 3 feet apart within rows with at least 6 feet between rows. Set each plant at the depth it grew in the nursery or pot. Soak the soil thoroughly with water or a mild fish emulsion solution, making sure that no air pockets are around the roots.
Young plants must have water. Newly set plants should be watered every three days for four weeks, unless it rains heavily. Feed them once a week with a liquid fertilizer solution. If possible, a trickle irrigation system should be used when less than one inch of rain falls per week.
With potted plants, no pruning is necessary, but bare-rooted plants need to be cut back to 2 to 3 inches above the ground when you set them out, because the newly established roots cannot support growth on longer canes. The result would be a weakened, stressed plant. Pruned plants will establish strong roots and plenty of strong canes for future berry crops.
Mulch your planting heavily. Thick layers of shredded bark, leaves, shavings or wood.chips are all excellent mulch material. Several inches of mulch will deter weeds and help regulate moisture. Some gardeners lay black plastic, landscape fabric, or cardboard between the rows, then cover them with mulch to prevent weed and raspberry sucker problems.
You will need to provide some means of support to keep your raspberry canes upright. Some gardeners tie the canes to stakes or posts placed every 2 to 3 feet along the row. Others put a fence consisting of strands of smooth wire on either side of the row. If no support will be provided, cut the canes back to 4 to 5 feet in height in early spring to stiffen the canes, which will then be less likely to fall over.
The floricanes die within weeks of bearing fruit. Remove these canes every year, otherwise the plants will decline rapidly. As your patch matures, more pruning may be necessary, as the plants will produce an abundance of primocanes. In fall or winter, thin these canes to the strongest, allowing 6 inches between canes (see sidebar). Otherwise the, berries will be small and few. Keep rows no more than 2 feet thick for easy harvest, pruning, and better air circulation. Pruned canes should be burned or removed from the area, since they can harbor next year’s crop of insects.
Harvest occurs in July and August. An extended harvest can be attained by planting early, mid-, and late-season varieties or fall-bearers. A truly ripe raspberry will come off its receptacle with only the gentlest pressure. Pick into shallow containers as the fruit crushes easily. Move freshly picked berries out of the sun as soon as possible, since fresh berries mold rapidly. Chill and process them immediately.
Raspberries are susceptible to disease and insect problems. Good air circulation and a well pruned patch is your best prevention. Prune only in a dry patch; avoid rain soaked plants and dewy mornings. Look for signs of the following diseases in your berry patch:
Anthracnose – a gray splotchy, purple edged blight that shows up on the bark and leaves. Sanitation is the best prevention. Lime-sulfur spray when leaves are 1/4- to 1/2-inch long is also effective.
Mosaic and other viruses – leaves are marbled or mottled with yellow. Plant widely available resistant varieties. Remove and destroy infected plants. This disease is easiest to detect in spring.
Root or crown gall – fleshy, wartlike growth on roots. This soil-borne bacterial disease has no cure, so plant resistant cultivars. Once contracted, destroy plants and establish a new patch with resistant cultivars.
Rusts – occur more on black and purple varieties, appear as orange powdery spores on the underside of leaves. Remove and destroy affected plants.
Verticillium wilt – canes wilt suddenly in mid-summer and die. Remove and destroy affected plants. Avoid planting raspberries near nightshade vegetable crops (tomatoes, potatoes, peppers, eggplant).
The only insect of consequence in home gardens is the cane borer. If the tops of your young canes suddenly wilt and fall over, inspect them. You will likely find two complete circles near the top of the cane. Open the cane and you will find a larva. If left unchecked the larva will bore down through the cane, kill it and move on to another, with increasing damage to your patch as years go on. As soon as the wilted top appears, cut it off below the damage and burn the top.
The Hardiest Summer Fruiting Varieties
Boyne – dark red fruit, heavy bearer, vigorous.
Killarney – good flavor, midseason, red, hardy.
Latham – fair fruit quality, one of the hardiest; disease susceptible, so buy clean plants.
Reveille – good flavor, early season, soft fruit.
Taylor – excellent flavor, large fruit, midseason, heavy bearer. Hardy, but less so than some.
Some fall bearing raspberries recommended for Maine are August Red, Autumn Bliss, Fall Gold, Heritage, Redwing and Fallred.
Of the purple cultivars, Royalty and Brandywine are hardiest, though the latter is tart.
Yellow raspberries harbor more disease. Chose clean stock. Of the cultivars available, Goldie is most promising, with high yielding, 6-foot canes and golden orange berries.
With a few hours of annual maintenance and picking time, you can have an abundance of delicious berries for a year of fresh eating, then jams, pies, syrups and even wine.
About the author: Roberta has written about cultivating and cooking crops for The MOF&G for many years.