Mulching of raspberries has shown some benefit for most types of brambles. Root-rot-susceptible cultivars may be adversely affected by mulch after the first year.
Mulches are applied from two- to four-inches deep, either to the row area alone or to the whole soil surface. When both row areas and between rows are mulched, cultivation is eliminated. Materials such as straw, old hay, sawdust, and planer shavings may be used, but they should be free of weed seeds. Because mulches decompose, more material must be added from time to time.
It is advisable to practice clean cultivation after the plants are set. The plants have weak root systems the first season, and shoots may be smothered by heavy mulch. Mulches should be applied after the shoots have grown four to six inches and when the soil moisture is plentiful. Apply a residual herbicide before mulching after planting.
If there is doubt as to whether the advantages offset the disadvantages for a particular planting, it is advisable to mulch a part of the planting as a trial.