The 2012 ASHS Annual Conference

The Veterans Memorial Rose Garden at Mississippi State University is a formal rose garden where a large variety of roses are grown with access to both researchers and public visitors. Fifty-three cultivars of roses from a number of classes and grown on R. x fortuniana rootstock, ‘Dr. Huey’ rootstock or on their own roots are included in the collection. These roses were planted in spring, 2008 in ground beds around the periphery of the garden to demonstrate genetic diversity within the genus. Data was collected in November, 2008 and October, 2009 and included plant height, plant width, blackspot rating (incorporating both defoliation and infection), flower quantity and quality, foliage quantity and quality, and plant habit and vigor. The Horsfall-Barratt rating scale was used to generate scores for black spot (Horsfall and Barratt, 1945).  Quality ratings were based on a scale of 1 to 10, worst to best and also averaged to provide an overall index of quality. Data is analyzed using the Glimmix  and Corr Procedures of SAS. Growth types ranged from a large climber to a miniature rose. Plant height, is positively correlated to plant width(r= 0.68, P<0.01), volume (r= 0.84, P<0.01), and plant habit and vigor (r= 0.50, P<0.01).  Blackspot ratings also range greatly, especially since data is only from late fall when many roses are near winter defoliation and the climate has cooled. Blackspot is inversely correlated to flower(r=–0.30, P<0.02) and foliage quantity and quality (r= –0.59, P<0.01), as well as quality average (r= –0.46, P<0.01). Plant width is positively correlated to blackspot (r=0.27, P<0.04), possibly reflecting a spreading growth habit near the soil where spores can be splashed up. Flower ratings were biased towards roses that bloom well in the fall and near 1 for cultivars that bloom only in the spring. Flower ratings are inversely correlated to plant height (r = –0.29, P<0.03), volume(r= –0.36, P<0.01) and blackspot(r = –0.30, P<0.02). Flower ratings are positively correlated to foliage ratings(r = 0.32, P<0.02) and quality average (r= 0.52, P<0.01). Smaller roses are bred to be floriferous, and spring only bloomers tend to be large roses. High levels of blackspot appear to reduce foliage needed to support bloom. Plant habit and vigor ratings are positively correlated to growth, foliage and quality average to <0.01%. This information supports our efforts to determine sustainable rose cultivars suited for gardens in climates similar to east central Mississippi.