Primocane-fruiting raspberries (Rubus idaeus L.) produce new canes (primocanes) from buds on the roots or from basal buds on older canes or the crown. Flowers are initiated on these primocanes regardless of daylength and when field-grown can produce fruit within one growing season, usually in late summer or fall (Keep, 1961). Flowering and fruiting occurs on the distal buds of the primocane with proximal buds remaining dormant until the following spring, providing the potential for two crops per year. More traditional floricane-fruiting raspberries initiate flowers in axillary buds on primocanes under short days and cooler temperatures of fall, but a chilling period is required before these buds will grow. Consequently, axillary buds on floricanes flower and fruit in early summer of the second year. If given enough time, many raspberry genotypes will eventually initiate flowers on primocanes that have not been exposed to short days or cool temperatures, but these are not generally called primocane-fruiting types because fruiting does not happen within a typical growing season (Jennings, 1988).
When fruited both in summer and fall, crop quality can be reduced relative to a fall-only crop (Pritts, 1989). Although double-fruiting is practiced in California, Chile, and some other warm regions where chilling hours are limited (Daubeny et al., 1992), many primocane types are fruited for the fall crop only. Because of their adaptability and ease of manipulation, growers have been able to achieve season extension even when fruiting for a single crop. These techniques, coupled with earlier and later fruiting cultivars with good fruit characteristics, are having a dramatic impact on the raspberry market. Fresh raspberries are now available every month of the year from U.S. sources (USDA, Agricultural Marketing Service) with much of the fresh market supplied by primocane-fruiting cultivars.
Dale, A., Gilley, A. & Kent, E.M. 2001 Performance of primocane-fruiting raspberries grown in the greenhouse J. Amer. Pom. Soc. 55 27 33
Dale, A., Pirgozliev, S., King, E.M. & Sample, A. 2005 Scheduling primocane-fruiting raspberries (Rubus idaeus L.) for year-round production in greenhouses by chilling and summer-pruning of canes J. Hort. Sci. Biotechnol. 80 346 350
Demchak, K., Lamont, W.J. & Orzolek, M.D. 2003 High tunnel berry production 119 126 High tunnel production manual Dept. of Horticulture, Penn State Univ University Park, PA
Oliviera, P.B., Oliviera, C.M., Lopes-da-Fonseca, L. & Monteiro, A.A. 1996 Off-season production of primocane-fruiting red raspberry using summer pruning and polyethylene tunnels HortScience 31 805 807
Oliviera, P.B., Oliviera, C.M., Machado, P.V., Lopes-da-Fonseca, L. & Monteiro, A.A. 1998 Improving off-season production of primocane-fruiting red raspberry by altering summer-pruning intensity HortScience 33 31 33
Pritts, M.P. 1989 Pruning and trellising brambles Pritts M.P. & Handley D. Bramble production guide Natural Resource, Agriculture, and Engineering Service publication 35 Ithaca, NY
Pritts, M., Hanson, E., Fiola, J. & Kelly, M.J. 1992 Rowcovers accelerate fruiting and increase productivity in primocane-fruiting red raspberries HortTechnology 2 46 51
Swartz, H.J., Naess, K., Fiola, J., Stiles, H., Smith, B., Pritts, M., Sanford, J. & Maloney, K. 1992 Raspberry genotypes for the East Coast Fruit Var. J. 46 212 216