July 18, 2001
Stillwater Gazette
Betsy Halden

Proper care of raspberries

Raspberries are one of the joys of our Minnesota summers. Fresh, succulent, juicy. I’ve been known to purchase a box at a roadside stand and eat them before I reach home. I’ve always considered myself fortunate to be the recipient of a jar of Ellie Bruner’s raspberry jam. In my opinion, anyone who has raspberry bushes has a very valuable garden.

Raspberry plants are relatively easy to grow. If you have considered growing raspberries here are some cultural procedures to know about. Cultural practices such as fertilization, watering, and controlling weeds, insects, and diseases help ensure healthy plants and healthy fruit. Fertilization. Established raspberries should be fertilized in spring before new growth begins. Apply 4 to 5 pounds of 10-10-10 fertilizer to each 100 foot row. Uniformly spread the fertilizer in a 2 foot band. If the raspberries are mulched with sawdust or wood chips, apply a slightly heavier rate, 5 to 6 pounds of 10-10-10 per 100 foot row. 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.

Irrigation. 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. During fruit development, raspberries require 1 to 1 ½ inches of water, either from rain or irrigation, per week. Insufficient moisture during this time may result in small, seedy berries.

Weed control. Weed control I raspberries is necessary to reduce competition for water, nutrients, sunlight. Cultivation and mulches are the most practical control measures. Cultivate the raspberry plantings frequently during the spring and summer months. Small weed seedlings are relatively easy to destroy. large weeds are more difficult. To prevent injury to the roots of the raspberry plants, don’t cultivate deeper than 2 to 3 inches.

Mulches help to control weeds and conserve moisture. Possible mulching material include straw, crushed corncobs, chopped cornstalks, sawdust, wood chips, lawn clippings, and shredded leaves. The depth of mulch needed depends upon the material used. Optimum depth ranges from 3 to 4 inches for fine materials, such as sawdust, to 8 to 10 inches for straw on well-drained soils. Avoid deep mulches on poorly drained soils to discourage root diseases. When mulching red raspberries, apply the full depth between the rows. Within the rows, apply only enough mulch to control the weeds so the new canes can emerge in the spring. Since mulches gradually decompose, apply additional material each year.

Insect and Disease Control. Good cultural practices should help prevent many insect and disease problems. Maintaining red raspberries in a 1- to 2-foot-wide hedgerow helps insure good air circulation and penetration of sunlight. narrow hedgerows dry quickly after a rain, discouraging disease development. Apply pesticides when insects and diseased start to cause significant damage.

Summer pruning of raspberries. To maximize yields, raspberries must be properly pruned in spring and summer. The pruning procedures for red, black, and purple raspberries are based on the fruiting characteristics of the plants.

Summer pruning of raspberries is vital. It is overlooked by many gardeners. After the last summer harvest, promptly remove the old fruiting canes of all raspberries at the soil level. Destroy the canes. Removal of the old fruiting canes helps control diseases. Their removal also permits more light to reach the new shoots which results in higher yields.

“Raspberries for the Home Garden” and “Raspberry Diseases” are two University of Minnesota Extension publications that give additional information learn about growing raspberries in our area. You can access them on the web at www.extension.umn.edu/distribution/horticulture/DG1152.html.

Betsy Halden is a Master Gardener with the University of Minnesota Extension Service. University of Minnesota Extension Service materials were consulted in the preparation of this column. You can reach Betsy Halden at eahalden@comcast.net