The impact of within-row spacing on the productivity of glasshouse roses grown in two planting systems

Stem yield and quality of roses for cut flower production were evaluated. T he plants were grown in two planting systems as an alternative to the tradi tional "vase-shaped" system. In the trellised system, two cultivars of Rosa hybrida (cvs Gabrielle and Kardinal) were planted in a commercial glasshou se in 3 m sections of bed. Within-row spacing was varied to give 6-16 plant s m(-2). After a three-month establishment phase the basal shoots were bent to an angle of 30 degrees above horizontal and restrained with a trellis w ire. Flowering shoots sprouting from axillary buds along a basal shoot were harvested at their lowest node, minimizing branching. Compared with "vase- shaped" rose plants at the same density, trellised roses produced 24% more basal shoots, 46% more flowering shoots (cv. Gabrielle) and approximately 4 6% less blind shoots per plant over five months. Phenotypic variation was g reater in cv. Gabrielle than in cv. Kardinal in response to within-row spac ing, as indicated by the number of basal shoots formed. Within-row spacing, over the range explored, did not affect the number of flowering shoots per basal shoot. Trellising rose plants increased stem yield and quality, but production over the long-term requires further investigation. The single sh oot planting system contained a mixed population of single-stemmed rose pla nts of Rosa hybrida (cvs Gabrielle and Gerdo). It was grown in a field over a range of within-row spacings to give 20-105 plants m(-2). Over three har vests, increasing the number of plants by 10 plants m(-2) reduced the propo rtion of flowering shoots by 4.4%. Expressed on a unit area basis, a five-f old increase in plants m(-2) produced a three-fold increase in stem product ion.