Growth Performance of Rose Cultivars In Raised Brick Beds

Thirty cultivars were planted in 2006 in a new formal rose display garden, and 2 cultivars were added in 2007.  Sixteen cultivars are grafted on R. x fortuniana rootstock, of which 1 is a Shrub (S) and 15 are Hybrid Tea (HT) roses.  Cultivars on R. x fortuniana rootstock are favored by exhibition rose enthusiasts in lower southeastern US for vigor and performance.  Thirteen cultivars are grafted on ‘Dr. Huey’ rootstock, of which 1 is a Grandiflora (Gr), 3 are Floribunda (F), and 9 are HT roses.  ‘Dr. Huey’ rootstock is a common understock for roses, particularly in hot climates.  Three cultivars are on their own root, of which 1 is a F and 2 are S.  Plants range from 2 to 6 per cultivar.  Data on plant height, plant width, number of canes per plant, and ratings for black spot, incorporating both defoliation and infection, were collected at end of growing seasons in 2007 and 2008 in November.  Horsfall-Barratt rating scale was used to generate scores for black spot.  In 2008, end of season visual plant performance was assessed by rating flower quantity and quality, foliage quantity and quality, and plant habit and vigor on a scale of 1 to 10.  Cluster analysis shows less distinct patterns for height and width for the combined 2007/2008 data than 2007 data alone for cultivars regarding rootstock, suggesting that growth differences become less with time and maturity. One-way ANOVA, run on combined data, shows a range of cultivar differences, but interpretation is difficult due to the nature of the collection. Pearson correlation analysis reveal significant correlation between mean overall plant performance and blackspot for cultivars on ‘Dr. Huey’ rootstock (r=-0.60) and R. x fortuniana rootstock (r=-0.61).  One-way ANOVA, separately analyzed by rootstock type, shows cultivar differences within rootstock selection.  This research project supports our expanding research program combining the best cultivars and environmentally sound, sustainable techniques to produce better roses for Southern gardeners. We will continue to display cultivars grown on both rootstocks and on their own roots to demonstrate a wide range of rose choices for gardens and landscape uses, and to understand what genetic and production forces shape the growth habits of roses.