Performance of 12 Shrub Roses Grown in Northern, Central and Southern Florida Under Low Maintenance Conditions

Sales and use of shrub roses have increased dramatically but information on performance in Florida is lacking, especially under low maintenance conditions. Twelve shrub roses were chosen based on availability and reported plant performance in Florida and Texas.  Clonally propagated, own root cultivars were obtained as bare root plants or in #1 containers.  Six uniform plants of each were installed on 23 Jan. 2008 in southern Florida (Fort Pierce; USDA Cold Hardiness Zone 9b), central Florida (Plant City; USDA Cold Hardiness Zone 9a) and northern Florida (Quincy; USDA Hardiness Cold Zone 8b).

Each location followed the same installation and management guidelines. Plants were placed 8.0 ft on center in compost-amended rows covered by a 4.0 ft wide strip of landscape fabric and locally available mulch. Roses were fertilized at planting and every 6 months with a slow release fertilizer (15N–3.9P–10K; 6 month formulation). The initial fertilization rate of 121g N-m², was subsequently increased in central and southern Florida in proportion to their longer growing seasons. Roses were micro-irrigated with 1.9 l-plant^-1 daily for 4 weeks and on alternate days for 8 weeks to establish plants and then weekly thereafter. Plants were pruned at 56 weeks (Feb. 2009) to remove 25% of the plant canopy.

Visual quality was assessed monthly on a scale from 0 to 5 where 0=dormant, no foliage present, 3= average, somewhat desirable form and landscape performance, to 5= very desirable form and landscape performance.  Monthly flowering was rated from 1 to 5 where 1=no flowers and 5=flowers found on 76-100% of the plant canopy.

After 2 years under low maintenance conditions, cultivars with average cumulative visual quality ratings of 3.0 or greater were Knock Out and 'Spice' in southern Florida, 'Mrs. B.R. Cant' in central Florida and Home Run, Knock Out, 'Mrs. B.R. Cant', 'Mutabilis' and 'Spice' in northern Florida. Average cumulative visual quality ratings less than 2.0 were considered unacceptable and were received by 'Old Blush' and 'Perle D'Or' in southern Florida and 'Belinda's Dream',  Carefree Beauty, Home Run, 'Old Blush' and 'Perle D'Or' in central Florida. Over the two-year period, Knock Out received the highest average cumulative flowering rating in each location. Other cultivars receiving an average cumulative flowering rating of 2.3 or more were Home Run and 'Spice' in southern Florida and Home Run in northern Florida. Ratings in central Florida were reduced due to damage from chilli thrips (Scirtothrips dorsalis).