FLOWERING AND FRUITING MORPHOLOGY OF PRIMOCANE-FRUITING BLACKBERRIES

Abstract

The flowering morphology of the erect, thorny primocane-fruiting blackberry (Rubus L. subgenus Rubus) cultivars Prime-JanTM and Prime-JimTM were studied in 2005 in Aurora, Ore., USA. Primocanes that were in early summer to 1 m were compared to un-tipped primocanes and floricanes. On average, soft-tipped primocanes for both cultivars developed five lateral branches, whereas un-tipped primocanes developed two lateral branches. Tipped canes developed almost twice the number of flowers as un-tipped canes. 'Prime-Jan' and 'Prime-Jim' began blooming on the branches of tipped canes in mid-July. Un-tipped primocanes began to bloom in late July. Apical branches on tipped canes bloomed earlier than branches on the mid and basal portions of the primocanes. Within a primocane inflorescence, the terminal or distal flower was always the first to open, followed by terminal flowers from axes located on the basal portion of the inflorescence. Flowers then opened acropetally within the inflorescence, with the exception of the most basal flower which was typically the last to open. In contrast to primocanes, floricanes developed two types of floral structures: short and long axial floral structures. Both types of floral structures developed below the spent primocane-fruiting apex of the un-tipped cane. Flowers on short floral structures began to open in early April while those on long floral structures began to open in mid-May. Days from anthesis to black fruit for soft-tipped and un-tipped primocanes averaged 46 to 52 d, depending on cultivar, and 57 d on floricanes. The blooming pattern within an inflorescence was the same for soft-tipped and un-tipped primocanes and floral structures on floricanes.