Spring-planted raspberries (Rubus idaeus L. cv. Malling Jewel) were exposed to competition from annual weeds for various lengths of time during the first growing season. Weeds germinating following crop planting in late March had no effect on numbers of new canes produced provided weed removal occurred by early June. The importance of preventing competition from these weeds during the critical period of cane emergence (June/July) was demonstrated. Dense weed cover reduced cane growth and, if weeds were left beyond late June, caused considerable mortality of planting material. Weed growth also frequently reduced cane height.
In the second year, all plots were maintained free of weeds. Fruit yields showed effects of weeds similar to or greater than those indicated by total cane growth in the previous year. Height of new canes was unaffected by previous weeding treatments, but the numbers of new canes produced continued to show severe effects of initial competition from weeds.
Allowing further weed growth to develop after initial weeding had no additional effect on crop survival or cane numbers in the first year. In one experiment, however, a reduction in cane height due to weeds germinating in June was followed in the second year by a reduction in the numbers of new canes produced.