Fertilization

Keep the planting completely free from weeds with shallow cultivation and hand pulling as necessary. Make sure the plants receive one to two inches of water a week for best growth. Mulch can be used to reduce weed problems within the plant rows and will also help retain soil moisture and add valuable organic matter. Spread sawdust, bark, pine needles or rotted leaf mulch over the plant rows, and maintain it at a depth of three to four inches.

Starting the second year of the planting, a cover crop may be planted between the rows. An annual cover crop may be planted between the rows. An annual cover crop, such as spring oats, can be sown just after harvest. The oats will aid in hardening off the raspberry plants for winter by using up excess water and nutrients in the soil and will also reduce weed growth. Oats will be killed by low winter temperatures, and the dead sod cover will reduce soil erosion in the spring.

A permanent cover crop may also be sown following harvest the second year. A non-competitive grass cover, such as a bluegrass-fescue mix, can be sown between the plant rows. Take care to prevent grass from spreading within a foot of the raspberry plants, or it will compete with the raspberries for water and nutrients. Permanent sod covers allow easy access in the raspberry planting, prevent soil erosion and weed growth and can be easily maintained by regular mowing.

Raspberries should be fertilized each year in the early spring (mid-April). Apply 20 pounds(9.1 kg) of 10-10-10 (or organic equivalents) per 1,000 square feet(93 square m) of the planting. Increase the rate to 25 pounds(11.3 kg) if a heavy mulch is being used.

Alternatively, the application may be split, applying half of the recommended amount in mid-April and the second half four to six weeks later.

Pruning

Pruning is a vital part of maintaining a healthy raspberry planting. This practice greatly inhibits the spread of raspberry diseases and improves fruit quality and yield. Pruning should begin soon after harvest is complete by removing all the canes that fruited. This improves light penetration and air circulation for the canes that will fruit next year.

Also, remove any new canes that are growing outside of the 12- to 18-inch(30 to 45 cm) row width, or show obvious symptoms of insect or disease damage. In the spring before the buds break, thin the remaining canes, leaving only four to five of the sturdiest per foot (30 cm) of row. Spread the canes that are left onto the wires of the trellis and tie them with twine or some other soft material.

Everbearing or fall-bearing red raspberries bear a late-season crop on first-year canes. If they are pruned in the same manner as the summer-bearing types, they will bear two crops per season; one in the summer on the second-year canes, and one in the fall on the first-year canes. Everbearing raspberries can also be managed to produce only the fall crop.

Simply mow all the canes down early each spring. During the summer, cut down any new canes that develop outside the 12- to 18- inch(30 to 45 cm) row width and thin the remaining canes to about six inches apart, leaving the sturdiest. This technique greatly reduces pruning labor, but also eliminates the summer crop. Unfortunately, most everbearing cultivars, such as Heritage, produce the fall crop too late in the season to escape damage from frost in most of northern New England.

For black and purple raspberries, pinch off the top four inches(10 cm) of new canes when they reach about three feet (1 m) in height. Blackberries should be pinched when they reach four feet(1.2 m). This encourages the canes to form side branches, or laterals, which will bear the fruit in the following year.

Remove all canes that fruited following harvest. In the early spring, thin the remaining canes, leaving only five to seven of the sturdiest per hill. Cut the side branches back to 12 buds (usually about 12 inches(30 cm) in length) and tie the canes to the wire or post for support.

Remove all plant waste from the field after pruning and destroy it, preferably by burning. Leaving dead canes in the planting will encourage the spread of disease.

Harvesting

Raspberries are ready to pick when they easily separate from the receptacle or core. Blackberries do not separate from the core, so ripeness should be judged by color and taste.

All bramble fruit are extremely perishable and should be harvested frequently. To maintain fresh quality, place fruit in shallow containers, no more than three fruit deep, and cool the fruit to 33 degrees F (1 C) as quickly as possible. Fruit properly harvested and held at this temperature can maintain fresh quality for three to seven days. If the fruit is to be made into jam or jelly, process it immediately, or freeze it until ready to use.

Pest and Disease Management

A well kept raspberry planting can provide fruit for 10 to 20 years, but viruses, fungi and several types of insects can greatly reduce yield and may destroy the planting if they are not controlled. Many problems can be prevented by proper planning and care.

Select only raspberry cultivars that are very hardy, and plants that are certified virus-free. If possible, destroy all wild brambles within 600 feet (183 m) of the planting. Encourage good air circulation by having at least eight feet (2.5 m) between your plant rows and keeping the hedges to a 12-to 18-inch(30 to 45 cm) width. Prune your plants regularly to promote healthy new growth and reduce the spread of diseases. Keep the planting weed free to discourage insect pests and prevent competition for water and nutrients.

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