Raspberries are relatively low-maintenance and can add bright color to your home’s landscape. Instead of buying raspberries in the grocery store, you can raise your own bountiful harvest in your backyard. To help maximize your harvest, incorporate a weed control strategy to minimize weeds that may compete with your raspberries for soil nutrients, water and even bee pollination.
For severe weed problems that mulching or tilling can’t control, herbicides can help. Generally, an application of glyphosate or a similar broad spectrum, non-selective herbicide before planting raspberries helps eradicate established perennial weeds. Then, gardeners can regularly use pre-emergent herbicides to keep weed seeds from germinating. Raspberry plant-safe chemicals often used to control weeds include isoxaben and propyzamide. For the best results, gardeners should use different chemicals each year to reduce the risks of creating herbicide-resistant weeds.
Mulch serves numerous purposes. It keeps the raspberry plant’s root network cool and locks soil moisture in the dirt while simultaneously adding nitrogen and other nutrients to the ground as the mulch decomposes. However, one of its most valuable features is the ability to block weeds from growing. For raspberries, Iowa State University Extension recommends spreading wood chips or crushed corncobs between the raspberry bushes.
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 .