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 destroyed easily. Large weeds are more difficult to control. To prevent injury to the raspberry plant roots, do not cultivate deeper than 2 to 3 inches.
Possible mulching materials include straw, crushed corncobs, chopped cornstalks, sawdust, wood chips, dried grass clippings, and shredded leaves. The depth of mulch needed depends on the material used. Optimum depth ranges from 3 to 4 inches for fine materials, such as sawdust, and from 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 of material between rows. Within rows, apply only enough material to control weeds, allowing new canes to emerge in spring. Since organic mulches gradually decompose, apply additional material each year.
Several herbicides can be used by commercial raspberry growers to control weeds. Herbicides registered for use on raspberries can be found in PM 1375 Midwest Commercial Small Fruit and Grape Spray Guide for 2004 .
This article originally appeared in the 7/2/2004 issue.