Four Rosa hybrida cultivars were grown in 100 to 500, 700 to 1300, and 1500 to 2500 ppm CO2 atmospheres for at least half the daylight hours from November to May. Production was studied continually for 24 months.
Numbers of flowering stems and lateral buds, fresh weight, and stem length were greater in CO2 supplemented atmospheres on hybrid tea and floribunda roses. Non-flowering percentages were lower for floribundas in CO2 enriched atmospheres. Greater leaf abscission and less root development were noted for hybrid tea and floribunda roses in 1500 to 2500 ppm CO2. Higher yields in non-CO2 supplementation periods (May to October) largely reflected growing conditions rather than CO2 effects.
Received for publication on April 28, 1970. Scientific Journal Series Paper No. 7202, Minnesota Agricultural Experiment Station.
Present address: Department of Horticulture and Forestry, Kansas State University, Manhattan, Kansas.