Raspberry plants are relatively easy to grow. If given proper care, they are also very productive. Important cultural practices include fertilization, watering, and weed, insect, and disease control.
Established raspberries should be fertilized in the spring before new growth begins. Apply 4 to 5 pounds of 10-10-10 or similar analysis fertilizer for each 100 feet of row. Uniformly broadcast the fertilizer in a 2-foot band. If the raspberries are mulched with sawdust or wood chips, apply a slightly heavier rate of fertilizer. Do not fertilize raspberries in late spring or summer. Late spring or summer fertilization encourages succulent, late season growth which is susceptible to winter damage.
Adequate soil moisture levels are necessary throughout the growing season for good raspberry production. However, the most critical time for moisture is from bloom until harvest. Insufficient moisture during fruit development may result in small, seedy berries. Raspberries require 1 to 1 1/2 inches of water per week, either from rain or irrigation, from bloom until harvest.
Weed control in raspberries is necessary to reduce competition for water, nutrients, and sunlight. Cultivation and mulches are the most practical control measures for home gardeners. Cultivate the raspberry planting frequently during the spring and summer months. Small weed seedlings are relatively easy to kill. Large weeds are difficult to destroy. To prevent injury to the roots of the raspberry plants, don't cultivate deeper than 2 inches.
Mulches help to control weeds and conserve moisture. Possible mulching materials include straw, sawdust, wood chips, lawn clippings, and shredded leaves. The depth of the mulch needed depends upon the material. The depth ranges from 3 to 4 inches for sawdust to 8 to 10 inches for straw. (When mulching red raspberries, apply the full depth between the rows. Within the rows, apply only enough mulch to control the weeds so new canes can emerge in the spring.) Since mulches gradually decompose, apply additional material each year.
Good cultural practices should help prevent many insect and disease problems. For example, pruning and removal of the old fruiting canes immediately after the summer harvest will remove potential disease inoculum and help control diseases. Also, maintaining red raspberries in a 1- to 2 foot-wide hedgerow helps insure good air circulation and penetration of sunlight. The narrow hedgerow should dry quickly after a rain, discouraging disease development. Apply pesticides when insects and diseases start to cause significant damage.