PERFORMANCE OF CONTAINERIZED ROSES IN A RETRACTABLE ROOF GREENHOUSE OR OUTDOORS

Flowering rose plants in containers can be produced by transplanting bare root roses in late winter into containers and forcing them to flower in a greenhouse or outdoors until they are ready for shipping. Two experiments were conducted to determine how plant development and performance are affected when containerized roses are forced in a retractable roof greenhouse (RRGH) or outdoors in full sun. The first experiment compared performance of Rosa ‘Mr. Lincoln’ and ‘Oregold’ plants that were dug from the field in January or February and were placed for 0, 4 or 8 weeks in cold storage before being potted and forced in a RRGH or outdoors in full sun. ‘Oregold’ plants forced in the RRGH in February after 4 weeks of cold storage flowered 6 days earlier than plans grown outdoors, but none of the other treatments resulted in significant changes in leaf emergence or flowering between the two environments. ‘Mr. Lincoln’ plants in the RRGH had more leaf area and greater stem dry weight than outdoors, while these variables were not affected for ‘Oregold’ plants in either environment. Water use differed by cultivar and was related to leaf area. ‘Mr. Lincoln’ plants had higher water use per plant, but less on a per leaf area basis than ‘Oregold’. In the second experiment Rosa cultivars ‘Oregold’, ‘Angel Face’ and ‘Chrysler Imperial’ differed in plant size, leaf emergence, time to anthesis, and flower number and size. Plants forced in the RRGH were taller, had a greater number of flowers with greater diameter, and earlier leaf emergence than plants forced in full sun. Water use of roses forced in the RRGH was on average 13% less than in full sun.